They won't fail.
Seriously. Scorpio and Neo are going to cost over $600, and still offer 1/3 the performance of a 1080/i7 gaming rig, which you could build for around $1000. Remember the PS3 launch? Now imagine if everyone interested in the PS3 already had a PS2.5 that could play all of the PS3 games, just with slightly crappier graphics. The already abyssal sales of the PS3 would be at least halved. This is the situation with the Neo/Scorpio. The only selling point these new consoles have is VR, which everyone hates and sees as a gimmick. (Except PC gamers, who are used to spending hundreds of extra dollars on gaming upgrades... By the time Scorpio and Neo are released Vive and Oculus 2.0 will be out, which means 1.0 will get a price drop.) These people will just buy a PC. (Probably with a 1070 or discounted 980)
Beyond that, about 3/4 of 360/PS3 owners haven't upgraded to the current gen yet. These people are primarily more casual gamers, and use their consoles more as media devices than anything. Given the option between an aging console from 2013 with not so much of a fantastic first party selection, and a brand new "casual" console with all of the same third party games + Smash, Zelda, Mario, etc at the same price... They're gonna choose NX.
tldr Nintendoomed thread #500, the answer is they aren't going anywhere. The Wii U was underpowered, and just had unfortunate marketing and timing. The same won't happen with NX.