I genuinely had to take a moment to even know where to start with this post.
First of all, tell me how on earth a developer can port a game designed with UE4 using UE3 as easily as they could using UE4 itself?, you see you have no clue about games development. These engines are a set of tools that make porting a game to different platforms as easy as possible. Having UE4 on a system isn't all about whatever knew effect you can pull off, its also about having the same tools on the system you're porting to as the ones you had on the system you created your game on.
Secondly what logic are you referring to? To make this as easy to understand as possible, Mark Rein of Epic said that while they wouldn't port UE4 to WiiU another developer could port it if they wanted to, their words not mine.
Yes its very likely possible that UE4 could be ported to 360, not that its even relevant to whether its portable to WiiU since, get this, WiiU isn't an XBox 360!