Who says the Shark is vapor? For almost 8 months people have being saying both the A1 and OS4 are vapor. Oh, but loooky...here they are. Vapor! is normally the cry of people who don't like something but can't find any good reason why they don't. I thought Codename Chicago was vapor - until out popped Windows95, the Abomination of Mankind. If the Shark fails to come out, AInc lose 1000s of potential customers of OS4. I doubt they will allow this easily.
As for emulation, correct - it can work both ways. But given what has gone before, i believe bplan will not want to emulate OS4. Some MOS folks have been rabid about wanting nothing to do with it, stating it as being coded by people who know nothing about the Amiga's insides and should go back to coding games. MOS and pegasos emulation on OS4 is the likelier prospect at the moment - especially if pegasos fails - which, let me just put clearly before the flames burn: I do not want to happen.
Lots of software on MOS - well, its mainly just direct ports of (fairly trivial) 68k stuff. I don't doubt that OS4 coders could hammer out the same stuff in a few months. So far, though, (and prove me wrong) there isn't anything in MOS yet that is truly great or innovative - apart from MOS itself. MOS has had at least a year. No games. Only one planned that I know (Feeble Files). And no big apps. Not good.