Can I port my Sprint number to google voice and then port it back into a new Sprint phone?

I've been a sprint customer for only 3 months so like many I was surprised the iPhone was coming to sprint. Of course i can't upgrade without paying full price for the iphone. So I was wondering can i port my number to Google voice..thus canceling my old phone..and get a new iPhone at contract price then porting my number back? Or am I kidding myself|||Kidding yourself.