The next wave of systems represented a setback for backwards compatibility.
When early pictures of the Saturn surfaced, rumors abounded that it
was backwards compatible with the Genesis because of the cartridge
slot. I personally recall hearing (uninformed) grumblings that the
Saturn was a Genesis/Sega CD/32X combination or at least backwards
compatible with them.
The Sony Playstation and Nintendo 64 weren't backwards compatible
either. The Playstation one goes without saying I guess. Nintendo
already established with the Super Nintendo that they weren't
interested in consoles being backwards compatible. I'm sure some saw
the d-pad on the controller and experienced a fleeting hope that
Nintendo made some kind of dream system that played it all. Keep the
faith, I'm sure some pirate system that does is in the works.
The next major system release was the Sega Dreamcast which was not
backwards compatible with any previous systems. Like the Sega Genesis,
backwards compatibility with the Saturn might have actually helped the
system. The Saturn was a pretty distant second to the Playstation but
had a few high profile games, like NiGHTS Into Dreams or Panzer Dragoon,
that would have offered some nice padding to the launch library. Sega
opted to try a fresh start and pass on any sort of backwards
compatibility.