I honestly don't think there's any kind of straight line from the 6809 to the 68000. They share little in common other than the '68' prefix and coming from the same company and being big endian. The instruction sets are very different. Designed by different teams. The peripheral chip set and bus management was different too.
The 68k shares more with 1970s minicomputers especially the PDP-11 and/or VAX architectures than any MPU that preceded it.
The 68k shares more with 1970s minicomputers especially the PDP-11 and/or VAX architectures than any MPU that preceded it.