Guys like Thrust were part of the original eHobby line. These were limited to 1,000 pieces. It's possible that they would get released into a TFC line because Sideswipe and Inferno were a part of this "limited" release too.

The TRU reissues on the other hand ... these were all limited eHobby releases:

Dirge (1,000)
Hoist (1,000)
Grapple (1,000)
Red Alert (1,000)


Some of the big name eHobby releases that haven't been touched:
Ratchet
Ironhide
Trailbreaker
Ramjet


Rumor has it, Ironhide and Ratchet will never see pressing again. Chinese bootlegs of Ironhide have surfaced and Takara doesn't want to reissue something that could easily be replicated.