I really do feel like now is the time to get a Wii U, because now the Wii U's life has really begun.
Yeah, the Wii U has been out for a few years, but Nintendo tanked on them when they first came out and Wii Us only really began to sell last year with the highly-anticipated releases of Mario Kart 8 and Super Smash Bros. Wii U. And with Amiibos having launched recently and new games on the horizon like Splatoon, the new Zelda game coming out for Wii U, Star Fox, DLC content for many games, and more, now is really the prime time to get one, in my opinion. I don't see Nintendo trying to force another upgrade this soon, because it wasn't until this last year that the Wii U actually really began selling well and making Nintendo money. They're going to want to keep that going for at least awhile, in my opinion.
And to be honest with you, I feel like the Wii U I bought last May was literally my second best purchase of the entire year. I've gotten so much out of it and even more games and content are well on the way.