I have a feeling that the Republican ticket will be Cain/Romney or Romney/Cain. It seems that if one of them become the nominee, the other one would be picked for VP.
Cain will not choose Romney as VP. A smart pres. candidate chooses a VP who (1) draws votes, (2) stengthens the team and (3) mirrors his life philosphy.
Romney will not draw votes from the Peoples Republic of New England states. Moreover, if he chooses Romney, he risks losing votes. Conservatives loathe Romney. Romney has no credible foreign policy experience. Finally, Romney is the antithisis of Cain.