Is it possible that asm.js, since it's compiled dynamically on the client (giving access to more information potentially leading to better optimizations) can eventually out perform c/c++?
The latency requirements prevent some of the more aggressive and time consuming optimizations from being attempted.
Obviously, those claims did not hold true in practice.
HotSpot has had some very talented people work on it. And Java bytecode is much more suited to such optimization than asm.js is, too. If it wasn't accomplished there, then it's doubtful it'll be done elsewhere.
So maybe it's theoretically possible, but we just haven't seen it happen in practice. There's little to suggest that it ever will happen, too.