I don't want it to be a failure. I think it has potential to succeed because Sony and Microsoft are effectively having soft relaunches of their systems at the same time. Making the timing of the NX less odd. Plus even though the PS4 Pro and Scorpio will be more powerful than their current models, Sony has at least confirmed that any game that is developed for the PS4 absolutely must be playable on the original PS4 and then will have extra options such as higher resolution for the Pro, supposedly this is a rule that will always be put in place, so unlike the New 3DS, no games can be exclusive to a Pro model. I imagine Microsoft would do the same with the Scorpio, but I've not seen any confirmation of this.
Anyways, as such, if the NX is effectively as strong as a standard PS4 or Xbone, and the porting process of games from those systems is as easy as has been rumored, then the NX could effectively live on as long the PS4 and Xbone and start receiving all those 3rd party titles the Wii U was not receiving. If that is the case, then the NX can have a fighting chance.
Having said that. Will it be a success or failure? I really can't say, but I have a feeling that regardless, when all is said and done, the NX will have the strongest library when compared to the PS4 and Xbone. Of course I think that's true when talking about exclusive titles with the Wii U compared to the PS4 and Xbone, by a longshot at that, but obviously, exclusive titles alone will not win you a generation as evident by the Wii U. Nintendo has to ensure that 3rd party support can happen.