I don't see any thing hindering a PPC daugther board for the FPGAArcade, except maybe, that some one needs to design and build it.
And yes, its true, that before we have it, we can't really be sure that its actually going to be made, but I bet that the FPGAArcade and the daugtherboard will be made.
I do not do bet or gambling, but one thing for sure if you ask me to hold my breath (seeing the record history in Amiga community with false promises) this is one with a risk too high for me to hold my breath.
I am not saying
ALL promises have being false...there is some promises where they became true: Minimag, ACA and naming little view...but those are not severe upgrades to go jumping about. But ones something like UltimatePPC and Natami comes as a major change to the community and the raw meat is put in front of us behind glass...we can never seem to reach it. I hope FPGA Replay will not be that raw meat.