I haven't confirmed that though. But hardware capabilities wise, the Wii U has the guts to render 4 content, it's just a matter of playing with the resolutions, what the TV shows, etc.
But certainly not 1 720p current gen pretty content + 4 480 intricate (3D scenes) content, and apparently not, in the context that i've so much stressed about, 1 current gen+++ game in 720p + 2 480p current gen other views of it. Even if the rumors of 2 padlets support happen to be true, let's say you play a third-party title on Wii U, if this game feature a cooperative mode, the system won't have the capacities (again in this environment) to render a 720p beautiful game + 2 other views for additional players, it will be 1 pretty 720p content + 1 480p.
Maybe with the final dev kits, with first-parties games, etc, the system will be capable of that.