If Nintendo wants to develop a Mario game using Unreal Engine 4, hey, they can get it for free — well, so long as Epic Games gets 5 percent of the gross revenue it makes more than $3,000.
Even as a novelty it probably would, and though Epic can cut side deals for big players who use the technology, licensing and royalties would probably be the hardest part of bringing Mario to Unreal 4. The game itself would figure to be no problem, judging by this demo reel from YouTuber aryoksini.
Mario is leaping and yahoo-ing around inside a variety of environmental assets available with a UE4 license. The animations are all created from scratch and pre-scripted.