Tristan,
Max is the "lead" developer at the moment. It is correct that for some parts of the team, interest has dwindled, but things are still going on, and developers are still working - for instance, I know that Peter is working on the Nvidia jetson board to integrate with AQ, and Menno will probably soon post an updated Hott version, based on the next branch.
In terms of releases, the "next" branch from Max is the the "official" release at the moment. He is pretty fast to fix reported and understood problems, but he is a one man army...
We are always looking for help; both people that can code, but also just in terms of writing documentation and helping out on the forum.
A number of universities are working with AQ - most noteably SDU Drone Center (University of southern Denmark) is full on into AQ. I am involved in a major research programme with them to build longrange BVLOS capabilities, and they are also working on indoor swarming and navigation, RTK and other interesting things. As they are a public university, all HW and SW that can, will become open source. I expect that we will see interesting new things coming from these projects.
So put put it plainly, AQ is very much still alive and I expect us to stay that way for a long time still...
I regard the latest releases to be very stable, and I think we gradually see more and more features integrated into the "next" branch, but really that is Max´s perogative to give statements on.
As for Quatos, all questions should be directed at Drone-Controls and Srinath. Quatos is a commercial 3rd party addon for AQ, and is not directly supported by the AQ team. I cant speak on their behalf!
The last AQ6 boards will be made available next week. A number of them is already reserved for existing customers, but there is gonna be some available for general retail also.
ESC32v3 will also be available from next week. In fact, I received the first sample shipment from iRC electronics just yesterday, and will make them available soon as possible....(need to coordinate with iRC and Flyduino). I do expect to see availability become more steady, now that iRC has taken over the production.