This linked issue is - quote - "a non-exhuastive, basic checklist of where we are aiming". As in, a checklist for MVP level support. And indeed, we have pretty much reached the MVP level, with several simple games (and some nontrivial libraries like box2d or mochicrypt) working.

From this point on, it's hard to make a simple TODO checklist. We could analyze the entire Flash API surface and make a tracking issue for each available class, but that's a lot of bookkeeping and it doesn't really say that much about real support (as, assuming pareto principle, 80% of fancier features are used by only 20% of games).