when mike is sitting there on his own in part 2 i always thought that he was already regreting what he had done. For me there was to much of a time jump to part 3.
That's exactly what FFC had in mind when filming the end of GFII. Look closely, Michael looks as though he's aged somewhat, and he's thinking back to when they were a family, now sitting there all alone.
FFC never had ANY intention of making a GFIII. The ending of GFII, as far as FFC was concerned, was going to be it.