We'll add a Wii U exporter as soon as we can. I don't know what Nintendo's process is though, so I can't guess at how long it would take. Once we have the SDK it should make the next beta release, unless Nintendo have issues with us making it publicly available.
Good canvas2d engines do implement memory management, but the peak memory usage is higher and it's less efficient, since it uses a system where old images that haven't been drawn for a while are released if it runs out of memory. Only CocoonJS/XDK have been problems in the past since they didn't even do that in canvas2d mode.