The only way Clark will be seen as Superman in Smallville
is in the last scene of the series finale. Other than that it's not going to happen.
I don't think a new movie will have any impact on whether or not Smallville
gets a 10th season. Its 10th, and certainly final, season would be over well before a new movie is released. From what I've heard there hasn't been a 10th season renewal yet because there's still some contractual haggling going on.