@bit I’m not an official of any sort just a regular here but I do recall David saying that Alpha 2 would likely run concurrently with Alpha 3 (to test data chains part 1). I think the point of this is Alpha 2 is very much for developers to test their apps on and for the public to see what devs showcase and test themselves, where Alpha 3 might be suited for data chains (part 1) testing such as IoT. How far away is Alpha 3? I don’t think anyone can pin the tail on that donkey 
but the team has been growing and their progress is starting to seem exponential. Just keep in mind a lot of unforeseen things can happen that alter plans and this is all just stuff I’m regurgitating the best I can that I pick up here.
So that and the fact there was some flack given for Alpha 1 coming down early is a good indication of it being up until it’s time to make a bigger leap, my guess is Alpha 2 & 3 will come down for Alpha 4.
Read this a couple posts down Will alpha 2 be online for an extended period of time once released? - #3 by dirvine