Let me try to answer your questions.
Yes, the framework is majorly maintained by couple of us. However, it is not the first time that a single individual is creating and maintaining a framework.
Personally I am a person, who loves to work in silence and make real progress on ground and not on papers and same is reflected on the framework, but I welcome everyone to share their thoughts and ideas and work on them when it’s the right time.
Progress seems stalled. Adonis is divided into many sub repos and all repos cannot have something meaningful to be added to them all the time. However, the current version of the framework is open for bugs and security related fixes.
We are planning a new release
5.0. Here’s some discussion on same https://github.com/adonisjs/discussion/issues/62 and also we have started the RFC process for 5.0 https://github.com/adonisjs/rfcs.
Will framework be around for next 2-3 years. Google has just shutdown their Inbox. No software comes with the guarantee that it will be around for any number of years. However, I do get your point.
Their are some great projects like https://cmty.app/ and companies like http://kayako.com/, who uses AdonisJs everyday. So I have no plans of stopping the development in near future.
However, I have a fulltime job and I work in phases. The day I will start committing changes in Adonis, I will do that for months and then I will focus more on my job after that. (I have to balance).
I hope this helps you in making right decisions.