Unless AROS for PPC has binary compatibility with MorphOS and/or OS4 software and seamless 68k binary compatibility too then there isn't much point in it really.
If it did have those things I'd definitely use it on PPC though. Maybe ARIX for PPC will have all those things? Here's hoping! 
Something like Petunia is not very propable because of lack of developer resources. The same reason why MorphOS team will drop that for the new ISA too. Arix solves some problems, expecially missing drivers and implements some sort of SMP (as I understand it) but it will not offer something like "Petunia". That is the price for getting affordable good hardware, you cannot have all, at least if the numbers of developers is so limited. With enough money everything is possible of course but we do not need to discuss about that

. So in short: do not expect that.
Binary compatibility with MorphOS and/or OS4 software? How should that work at all? All are different on API level