Setting the "vaporware" aspects aside, I would say there's a good chance this machine will run some rebadged OS referred to as OS5. If for no other reason than the ownership of OS4 coming into question.
I wouldn't at all be surprised to see this thing running QNX actually, reverting to the original planned rebirth of Amiga. At very least a Quark kernel running an Amigaesque X interface. Perhaps a modified BSD, like OSX.
That would be the simplest solution from a business standpoint. Abandon all backwards compatibility, abandon the old OS. Move forward with new hardware and a new platform.
Will WE be happy? No. But since when has that stopped them? And they're right to ditch the old crap in lieu of a completely new platform, with serious specs. Maybe :-o Make some money??