This prediction would be as plausible as Nintendo exiting the home consoles business.
What you "doom" guys dont get is that, if Nintendo drops the Wii U, its all over for them in the home console market. There is no recovering from that. No one will trust them enough to buy their new system, just like with SEGA in the past.
I think Nintendo will keep supporting their systems, but will probably move their virtual console stuff to smartphones, and if they are smart, their next system will be 2 in 1 portable and home console. There is no point in rushing to new failures. These systems they have out will only increase in userbase, theres no point in starting over and undermining the new system. It would be a dumb business decision.
Only way i see this happening is if Iwata was fired and they got a dumb new CEO in that is gonna run down the company for good.
That beeing said, they can do things for the Wii U that isnt just trashing it. They can keep coming up with good games, like Sony did with the PS3. It works on the long term. Also, they can redesign it, to make it more appealing to the consumer. Smaller gamepad, a bit more storage, new colors, special editions like they did with the 3DS aswell.
As they do all this to recover the current situation they should plan for the next cycle carefully.