The only ones that I think that would be considered "very likely" pieces of a rebuild that could contribute on a championship team a few years down the road are:
Rondo, Bradley, Bass, and Steimsma.
None of the others have shown over a consistent amount of time that they could make the top 12 of a championship caliber team. Rondo of course is the only one consistently playing at a championship level player over his career to date, but Bradley at least shows he would be worth a bench role on that level squad, Bass as well, and Steimsma has at least the ability to be a 3rd stringer on that squad and hopefully if he continues to develop at least a 2nd stringer. Starter would be nice! Jeff Green would be on that squad as well, but I am not sold that he will for sure return to the C's. Hope so, but not convinced.
JJJ may one day show that, Moore as well, but outside the big 3 and these guys we have no keepers.