Death note???!
Question: Did Raito really become a shinigami??
Answers: Did Raito really become a shinigami??
No.
There was some theory about Ryuk having promised Raito this, as he assures him he'll enjoy the afterlife, but remember that it has been said earlier in the series (when Raito questions Ryuk about heaven and hell) that humans reach an equal state after death, a state of nothingness, and there is nothig to imply that Raito was given special treatment by Ryuk, or that Notebook-holders go someplace else.
And, the epilogue of the manga doesn't hint at something of the sort. So there isn't really an proof for this theory- we don't see Light writing in his notebook in ShinigamiLand, do we? :)
I think it's better that way....
no
Nah, didnt happen.