I read online today that the SNL producers actually want Tebow. Man, they have no shame. Anything for a ratings boost.
In the article I read the "SNL source" claiming to want Tebow on the show was anonymous, and it was just some celeb cyber-rag. It's possible that Tebow's publicists planted the story. It wouldn't be the first time some celebrity campaigned to get on the show by planting rumors that they might host.
As you say, it would be strange of SNL to have him host since he's had a mediocre season--and career so far--as Denver's QB. They'd be inviting him only because he's outspoken about his faith, which could be a little dicey.