I bought a nodded Wii on here from someone a few years back. It has about 75% of what I want on it, so it was a good purchase. However, the 25% it is lacking does kinda drive me nuts, especially since I have no clue how to put anything new on it.
Wii U is an incredible system. Easily the best system of this generation and my most played hands down. Splatoon alone has gotten more time than my PS4.
When NX comes out there will be clearance, because Nintendo won't have the clout to have shelf space for 2 systems at most retailers. However, since there weren't as many Wii U systems made and because rumor states NX will not be compatible, I imagine any clearance will go quick.