When I went to Target this evening the Xbox One version rang up $29.99 even though it was marked $49.99 on the shelf. So if you can't get the PM and preorder, get the Xbox One version and preorder bonus since it trades in for $10 more at BBY.
The 3 game limit is per system, so you can trade in 3 copies of a PS3 version and 3 copies of the Xbox 360 version of a game. I have personally done this with Shaun White Skateboarding a couple of months ago.