The spin-offs could be awesome though:

Han Solo
Boba Fett
Darth Vader

It's got to be these.

Pre-TPM might not be as popular.

There remains the possibility that spin-off movies will be inspired by sequel trilogy characters:

Jaina and Jacen Solo
Corran Horn
Kyle Katarn
new charaters dealing with the Yuuzhan Vong invasion
Grand Admiral Thrawn
Mara Jade
Gavin Darklighter (if they don't choose Wedge and Tycho during or after OT)