The boards themselves have been done and sitting around for a LONG time. Mike should be checking in one of the last versions of the Floppy/HD support this weekend. It looks like the last AGA timing bug has been fixed. It's been demo'd all over the world running various hardcore AGA demoscene stuff, so it's quite compatible for sure. So, it should not be long.
There are already numerous arcade game machines done and available for it, along with a VIC-20 emulator and a C64 emulator that is nearly completed. There are plans for an Atari ST emulator (which won't be much of a stretch with the 680x0 core already completed for the Amiga emulation).