For personal computers, PowerPC is lying in its death bed. For servers, and consoles, it doing great, but neither are much use for us. So that leaves a few, specialist boards, which are released infrequently and cost a lot, and often have the Amiga aspect as a secondary reason to exist, behind a primary as an industrial control board, etc.
There are two potential future paths. x86 (might as well go straight to x86-64 and never deal with the crufty 32-bit stuff), or ARM.
I can only think how nice an AMD Brazos based mini-ITX board would be next year with AmigaOS. Single-chip dual-core CPU and Radeon HD graphics (not going to set the world alight, but cheap_)...
Or how about an ARM System-on-Chip? NVIDIA Tegra 2? TI OMAP? Marvell? Or dozens more ... these are getting to the dual-core, 1.5GHz+ arena now.