When is minecraft coming out for wii u on disc? Not to download from eshop?

I don't think that it is.

At this time, there's no official word from Mojang for a physical retail release for Minecraft: Wii U Edition. Mojang & 4J (who manages the console versions) is more focused on getting the Wii U version up to the same core version that the other consoles have (v1.8.8 -- Wii U version is starting at v1.6.4) so that all the consoles are in sync with each other BEFORE releasing a physical copy.

On a more honest, personal opinion… A physical copy is generally the best medium for a game that keeps evolving, as you'll have to grab updates online to get everything, so why bother?