As many have noticed, it has been many months since the last pre-alpha release, and nearly a year since the last stable release. To begin, I will attempt address some common questions about this release, and the status of Mindustry in general.
Up until this point, all (pre-classic) Mindustry updates have been incremental additions or changes to existing content. Everything I've made has been designed to fit in with existing blocks on the Serpulo planet campaign.
In v7, this is no longer the case - I am adding an completely new planet - Erekir - with its own unique set of blocks, environment tiles, units, turrets, transportation, etc. Aside from certain items, everything is different - there is no re-used content from Serpulo, not even walls or conveyors.
This is a little bit like making the entire game over again. When it is complete, it will be the biggest single content update in Mindustry history. To give you an idea of the content volume, there are currently 70+ new build-able blocks that have been added when compared to the last pre-alpha, with more than 130 new blocks added total - and I'm still far from done.
In addition, I am making significant changes to many various mechanics (again) - the campaign, unit control, and logic, for instance. Keep reading for more information on these topics.
With all of these factors combined, this update will take much longer than normal to complete. Please be patient.
I really don't know. While I already have a fair bit of content complete, I would estimate that it's only half done, if even that. Many mechanics are still in the "prototype"/"brainstorming" phase.
All I can say is, don't expect it anytime soon.
As mentioned above, I'm still early in the process of implementing content/mechanics for Erekir - it is not ready for testing, and will likely not be for a while to come. I would like to have the entire campaign complete before I even release an alpha build.
In short: Again, I don't know.
Below are some sneak peeks at content I've been working on. This is by no means a comprehensive list. Keep in mind that these units can (and have) changed significantly over the course of development - the final version may be radically different, or removed entirely!
Note: Many of these GIFs are taken from the #dev-previews channel on the Mindustry Discord. Consider following that channel for more frequent updates.

The T1 core, and its corresponding core unit. This unit can repair blocks, but does not have any offensive capability.

Shielded walker unit. Only blocks projectiles from the front. Very much WIP - weapons and legs will likely undergo significant changes prior to release.

Small insect-like unit. No special abilities. Demonstrates a new unit animation system.

Hovercraft. Missiles are technically units that can be targeted, and will follow the player's cursor.

Yes, I'm finally introducing tanks. This further demonstrates the capabilities of the new unit animation system.

A smaller tank variant.
As mentioned earlier, Erekir will have a completely different set of blocks from Serpulo. The production/crafting tree is still a work-in-progress, so I will not be showing it here, but here's what some of the distribution systems look like at the moment:

Ducts transporting items to Duct Routers. These routers only accept from one direction, and can double as sorters when an item is selected.

Duct overflow gates. Only accept from one direction.

Duct bridges. No linking or weaving allowed; output only in one direction.

Duct unloaders. Only input and output in one direction.

Beam "drills", connected with new orthogonal power nodes. Note that, while there are still certain ores on the ground in Erekir, beams are the primary way of gathering resources.
As many of you may know, unit control in Mindustry is terrible. As of the latest available version, there are four ways of controlling units, all of them with significant flaws:
Something had to be done. Thus, I have made the following changes:
I've been hinting at adding them for a while, but after experimenting with the mechanics, I am confident that RTS controls are the best way forward.
Here's how this looks in-game, so far:

Now, I know that this raises numerous questions, such as:
I will not be answering these questions, as I don't have a good answer to most of them - and even if I did, my answers could change over the course of development. All I will say is that, at the moment, I am trying to keep things as simple as possible. In my testing, even the current bare-bones RTS control system is worlds better than anything the game had previously.
This is a relatively minor feature I've been developing for use in campaign maps. Essentially, they are processors for scripting maps. These can only be placed or interacted with in the editor, and are for map-makers only.
World processors can currently do the following things; I may add more functionality as necessary:
World processors are meant to be placed in a corner of the map; while they are blocks with teams, they cannot be accessed, shot, broken or hovered outside of the editor. Note that they are simply logic processors with special instructions - this is not a new language or scripting system.
Below is a simple demonstration of a "cutscene" implemented with a world processor. Note that the trigger is a button for simplicity, but in most cases, you would have the trigger be something else out of the player's direct control.

Some examples of what can be done with world processors:
In addition to all of the above, I've also been working on improving the modding API, fixing inconsistencies, and adding more features for modders to utilize. Unfortunately, this also comes with the downside of breaking the overwhelming majority of older mods - after discussing this with the community, I've come to the conclusion that this is the only way forward.
Here are some examples of changes I've made so far - everything is still subject to change. If you're not a modder, feel free to skip this section.
Turrets, units, and weapons now support animation parts. These can rotate or move individually depending on their progress value, which is usually the weapon warmup or reload.
Close-up of the tank shooting animation:

Code (minus the blades, which are defined in a loop):

Weapons and turrets have long suffered from an inconsistent feature set and API. I've attempted to improve the situation by implementing a unified system for bullet patterns and shooting behavior.
This means:
As an example, here's what the new Swarmer bullet pattern looks like:
'shoot' is a field of each Weapon and Turret that defines its bullet pattern. This defines a 3-barrel shot pattern.

Result:

It is also possible to chain together shot patterns, to make things like this (demonstration only!):

Bullets can be created with custom movement callbacks. This pattern, for example, creates two bullets that move in a helix:

The block consumption system has been rewritten to allow for:
Most old generator classes - SingleTypeGenerator, BurnerGenerator, ItemLiquidGenerator and DecayGenerator - have been replaced with a single class, ConsumeGenerator. As an example, here's what the new definition for the combustion generator looks like:

The DrawBlock system has been expanded to support more block types, including generators, pumps and turrets.
This means that it is no longer necessary to extend these classes for custom drawing behavior. All drawing-specific GenericCrafter subclasses (Smelter, Cultivator, ...) have been removed. In addition, all DrawBlock subclasses have been made modular.
For example, this is how a smelter draw implementation can be defined on a GenericCrafter (or generator):
