Honestly, if Cain can get through Overeem and maybe one or two more guys (Werdum, not sure who else), I think Bones would be a really interesting fight.
Jones has very solid cardio--5 rounds with Rashad and 4 with Rampage and didn't appear tired in either fight. Cain might wear him down, but Jones probably has better cardio than any current HW besides Cain. (Cormier and Barnett also had good 5-round cardio, but Cormier won't fight Cain and Barnett isn't even in the UFC yet).
If Jones can defend TDs relatively well and fight decently off his back (he has the long limbs to be Anderson Silva-ish), it could be really interesting. Cain's pressure vs. Jones reach and unpredictability. If Sonnen were somewhat larger (say a 6'3" 245 pound natural HW), he might gives Jones the same challenge that Cain would, but I don't think the actual MW/LHW Sonnen will be able to work his pressure game.