Before you start porting. Better get some reasonable PPC-emulation (like Apples Rosetta) done. It would be a bad upgrade path, if all current OS4 binaries didn´t run.
Furthermore I don´t think Hyperion would hire on voluteer basis. Remember that OS4 is not open source. If you are looking for an open source implementation of the AmigaOS API, you should ask for AROS volunteers.
I suspect that in the long run, x86-versions of the Amiga API will be based on a Linux-Kernel as a kind of driver-engine. (Isn´t that what ICAROS is about? no?)