There was a time I would have really hoped for that. When Github was still new and the only, pathetic, alternatives were SF and Google Code. But back then, Google had its head stuck all the way up SVN's trunk.
Now I really hope they don't acquire Github. No website I know of has improved in such a consistently good way. Pure UI improvements, awesome new features and no feeling of feature creep on the user side (I don't feel overwhelmed by Github's features at all, I just want to try them all!).
Google does a decent job on their apps but I honestly think Github is a much higher quality shop: do one thing and do it extremely well.
With all that said, how much Google uses Github has little to do with acquisitions. They also use Twitter and you won't see them acquiring that.
It reminds me of the YouTube story. Google tried to do the same with Google Video and finally gave up and bought YT.
Google tries with Google Code now, but GitHub has probably much more traction. So, you may be right. I'm just not sure if they would do it, because the monetization is different. Or will we see AdSense inside GitHub pages for open repositories ;)
Probably does not make sense to them, most GitHub users are programmers who surf the web with ads disabled.
