The OP didn't ask about Nintendo Network, that's an entirely different thing but I guess the answer really lies in the fact that when they do finally close the servers, someone will have to announce that they will host a similar unofficial service.
Unfortunately my crystal ball won't work to show the answer so until we see an announcement from someone then the answer is no.
I'd like to think someone would if they could but Wiimfii requires a patched cIOS for the redirection of data to the custom servers and I don't think we have that access on Wii u yet.