Of course it won't be discontinued. A company would only do it with a console/handheld if they decide to leave the market like Sega. If 3DS and Wii U had flopped, then maybe they would be forced to leave, but even then I think Nintendo would survive (now, two gens in a row with both flopping would be to much).
Let's say Wii U does GameCube sales level (that's pretty much the worst case). Then, Nintendo will probably launch a successor in 2017-2019 and discontinue Wii U a year latter.
So it is secure. About sales, I don't see it improving a lot. The launch of both competitors with tons of AAA exclusives and massive third party launches with a lot of advertisement and stealing all media attention will probably kill any chance to reach higher sales.
if the bolded was true it would have relevance.
PS4 AAA Exclusives: Killzone Shadow Fall, Deep Down
XOne AAA Exclusives: Ryse, Forza
3rd party AAA: CoD Ghosts, Battlefield 4, Assassin's Creed 4
I could list more, but that's already a lot of stuff. The 3rd party offer contains some of the highest selling franchises now. Wii U gets some of them, but the best versions will be on PS4/One. Killzone is getting a lot of media coverage and Forza too (as the new IPs are). The preorder numbers agree, it will be a massive launch for both consoles. And at the begining of 2014 we will see Driveclub, inFamous, Titanfall, Destiny, etc.