The nVidia "Denver" project sounds pretty promising. While I think ppc has still a few cards to play (most notably QorIQ with Altivec) I think ARM will have the brighter future because NVidia tries to go the classic computer way additional to the embedded territory. Also ARM has the current buzz - and it is always good to join the buzzing bandwaggon if you also want your share of the buzz..

One of the most critical questions for a hypothetical MorphOS ARM route would be: Will Denver offer a big endian mode? Not all ARMs do offer this feature - but it is critical if a hypothetical MorphOS ARM should get legacy 68k/ppc compability.

If there is no big endian mode avialable ARM has no benefit over x86.

But the biggest question of it all: Who's gonna provide the team the required resources (time, time and time as well as a little incentve money and a few devices). Let's see what comes after the Apple ppc gear is maximally covered (Powerbook, iMac g5, Powermac g5) - and I don't think this is going to happen before 2012.