So you checked that AmigaOne, but there's a couple of other projects going on aswell that are targeted mainly for AmigaOS 3.1 - 3.9.
First (and for me most interesting!) project is Natami, work-in-progress that will be the new "classic" amiga when it's released
and there's Minimig AGA that seems to be progressing nice
For AmigaOS 4.1 there will be AmigaOne X1000 but for that i'll not hold my breath, but people interested in it will likely be excited