Dotn worry, there are plent of reasons to believe that Amiga Inc do plan to target more platforms then just the PPC platform.
That is, AmigaOS at version 5, will be so portable, they could target several platforms within only a small number of releases after version 5 without much effort
Mind you, it wont be completly portable but lots of parts of the system will be! - well, thats most peoples theorys anyway. It would be insane not to do that. Based on what technology is avaliable to them in OS5.