There are actually at least three types of HF torsos that I know of that appeared in sets, so I'm a bit confused. (For the record I own two, on Speeda Demon and another on Stringer, and I know Thornraxx has a different one.)
Thornraxx actually has a "torso" that isn't constructed out of typical torso beams. XT-4 has a different, smaller torso piece than other sets, and I like that piece a lot.
But that just brings up why I'm in no hurry for the current torsos to be replaced: each one has a unique use, and each of them is quite good for that intended use. They don't need to be replaced if it's only for freshness' sake, and the only reason any of them would ever need to be replaced outright is if a new one could be introduced that is so much more versatile that it renders the old ones obsolete. And I just don't see that happening any time soon.
Edited by Lyichir, Jul 26 2013 - 11:41 AM.
Proud attendee of the Bionicle panel at NYCC and after-hours Lego store event! Feel free to PM me any questions about Bionicle 2015 sets or parts!
Formerly Lyichir: Rachira of Influence
Aanchir's and Meiko's brother