I haven't heard of any plans to release a new version of the AmigaOne. I would guess 12 months after the release of OS4 that Eyetech would be wanting to perpetuate the market with a new version motherboard, but given the current lack of decent motherboard chipsets for PPC, I think there'll only be a CPU speed increase plus extra motherboard features, rather than important things like decent DDR support.
AFAIK the AmigaOne mini-ITX is in the prototype stage isn't it? Bear in mind that'll be effectively a severely cut-down XE.