You could very well be correct. Plus, I can see Herman possibly picking Gingrich as a running mate, since Cain could probably benefit from Gingrich’s legislative experience.
Why on Earth would anyone think that Gingrich would accept the number two spot?
Gingrich is a career politician. He was Speaker of the House... two steps away from President. He's got a huge ego (like most politicians running for President) and his ego is larger than most given his resume.
Gingrich knows that he'd have to teach and coach Cain for at least a year, and I don't think he'd want to take on that task.
BTW, I'm a huge fan of Herman Cain.