At that point NX can be so many things that it's a little random to guess honestly.
If it is what i've personally always wanted, meaning a portable that is the only Nintendo console (for a while..), what are their options for a 149-199$ console..
I didn't follow android devices progress, but i would guess they can have something way more powerful than a Vita, with let's say same screen size/rez (which would be an insane gap for a Nintendo portable). Vita made us believe, for a short while that it was capable of PS3 graphics. It's far from that, but i'm pretty sure a modern portable from Nintendo could do the same with a WiiU.Meaning you'll have weaker models, but the IQ/size of the screen/good use of modern shaders will make them not that far visually.
People will say bouhouhou and that's the only nintendo console now ? That's a back step what a shame.
Then they'll realize, that 99% of Nintendo ips, Smash Bros included were played by a masssive margin on portable this generation, with dreamcast graphics on a 400x240 screen. Then they'll realize the new Pokemon has a 2 generation gap graphically, as the new Monster Hunter, as the new Yokai Watch, as the new DQ/FF remakes, Bravely Default etc.. All those games with WiiU- graphics would be incredible updates.
Then they'll realize playing Pikmin 3, or 4 on a portable is pretty awesome, and that a new Metroid on NX is actually the best looking Metroid we've had on any console, same for a FZero.
Then they'll think, oh shit i'm i really playing an open world Zelda (this one will be tough to port) game in the Bus ??
Then they'll be playing Virtual Console of N64, GC on it.
All of this is possible and Nintendo needs do work on one little thing. Convince those 15-20% of Nintendo fans who think (nah i'm not playing a nintendo game on portable" that it's now legit, by letting them output to a tv, and/or buy a super xl sku, and/or letting them plug a cordless classic controller pro to it.
Oh and about third party, even if i think that's a fake problem. You can also see the thing from a portable pov. Ubi, EA etc couldn't port their next gen game on 3ds for obvious reasons ok. Then they could, but didn't bother to do it on WiiU, cause well.. the WiiU wasn't a success. Now, on a 3ds like (at least) level of success portable, with PS3/Wiiu graphic capacities (at least looks like it), wouldn't they be super happy to sell assassin's creed and Call of duty to kids ? That's a viable market.
I'll add that, most people sad with a underpowered machine are not the Nintendo fans who enjoyed a terribly good game library on 3DS, with everything they needed, a MK, a fire emblem, many marios, 3D and 2D, Pokemon, Monster Hunter etc... Those who didn't realize the 3DS was Nintendo's main platform and not something cheaper, weaker, but their base offer. And that offer was enough, in term of software, by a big margin. When you accept that, the idea of having what was the main Nintendo platform for 5 years making a 2 generation gap graphically, is kinda awesome.