I think Nintendo will do something with the Wii U-NX to ease the transition. Like maybe Wii U owners get a free game when they purchase an NX. That would go a long way to easing any bitterness. At some point too, I think Wii U owners have to grow up a little bit. Nintendo is a business and has to do what's best for the company.
Writing off an entire fiscal year, not being able to make dividend payments to stockholders, missing your profit targets, having your stock price suffer just so a group of Nintendo fans who are stomping their feet and insisting on no new hardware until they get their Animal Crossing and Metroid just isn't a sane way to run a business.
Nintendo needs NX out quickly so it can start an upturn in revenue and profit for Nintendo, and new hardware takes time to build momentum too (the first 6 months is usually a write off), so it would be more like Nintendo writing off two full fiscal years if they don't launch NX soon.
Nintendo last year made $350m profit..I think in Wii U situation, worst possible case would be to launch as soon as possible next hardware that isn't prepared too well. They need good and strong launch for hardware that dont have Wii U mistakes, for all that they need time.
They will release new hardware when they prepare all that properly, maybe will be end of 2016. maybe 2017.