I'd have thought the logical thing to do was bring out a cheap 1200/4000 based card for the classic users who want to keep their original cases, something like the
Dragon but without the busboard (basically an updated Blizzard 030 which supported more modern memory). This would need to be 100% compatiable with OS3.9 and the older software.
For PPC users, something like the proposed
Shark but with a modern PCI-E interface. Instead of mating it with a busboard there would be a new motherboard and case (based on PC tech). This board would be for running OS4.0 with 68k emulation for older tiles.
:-P