Doesn't work, the new iPad will not play videos with a resolution higher than 1920x1080, no matter how you get them on it.
I took a 4K video and tried shrinking and cropping it into all sorts of resolutions with Handbrake, and 1080p was the maximum it would play in the built in Videos App and also in VLC.
Unless someone creates an app that incorporates its very own video playing functionality (currently they all still use iOS's player shell, probably because it's the most efficient way) anything over 1080p is a no go.