>Do you mean left the 6502 as a co-processor or main processor? I hope you mean the former, because the 68000 was the only sane future for Jay and crew (even Atari, Apple, etc)
The former since the 68000 was definitely a faster and more powerful chip and there was no upgrade to 6502 that could match it. So they should have memory mapped the 6502 into the 68000 address space (64K chunk) and let old software continue to run in some mode like 8086/8088 DOS-based code still runs on Pentium 4 machines. Of course the custom chips would also have to map in there as well so the old software does not see that it's running in a new-processor machine.