Yup i get my Nintendo when the new Zelda games comes out, thats why i never got a Wii U. NX will probably be day 1 like the Wii of it has Zelda there.

Firstly kids can be Nintendo fans. I was a kid when I played N64 and fell in love with Ocarina of Time and Banjo Kazooie, I was 9 when I asked for a Gamecube for Christmas and only 14 when I got a Wii....

Also It reads as a silly statement to suggest almost "every" Nintendo fan owns a Wii U when its selling significantly lower then any Nintendo platform in history. Furthermore there is no basis for you to make that assumption. I'm simply telling you from my own experience that I know plenty of Nntendo fans like myself who do not own a Wii U and have no intentions of doing so. If you look at its sales numbers, logic supports my experience.

Secondly I made no statement about the 3DS' audience, simply that my friend was content with that system alone, but since you bring it up...When a systems sells almost exclusively on Nintendo titles (outside of Japan), I dare say at least half the people who own said system are decent fans of people behind the games their playing.

Finally you shouldn't confuse Nintendo fan with Nintendo loyalist, there is a lot of naunce in peoples taste and mine doesn't include much of Nintendo's current offering despite being a big fan of their IPs. Hyrule Warriors does not look like my thing although I would buy it for dirt cheap, remasters are not system selling points for me (played both Zelda games twice), not a huge fan of Mario World 3D's style (much prefer Galaxy style or classic -N64/Sunshine), Do not play Lego games, Not really interested in air combat games (StarFox- Liked SF Adventures though :p) although I would give this game a try if I had a Wii U, 2D Mario (NSMBU/Mario Maker) are fun titles but nothing that get me excited for a system and they would be low on my priority list, wouldn't look twice at Fast Neo Racing and Bayonetta looks cool but I couldn't be bothered to buy the first game on platforms I actually had so...

What did tempt me: Pikmen 3, Wonderful 101, Smash Bros, MArio Kart 8, Splatoon, Xenoblade (more so when it was first announced)

Nintendo fans can be complex ;)
(I'm also a fan of Square Enix, Sony, Bethesda, Bioware... a lot of different game developers)

And wii u's successor power in relation to wii u will be much higher than x1 vs x360. Also, less games to support with BC.

I think it will at the very least grant a good launch (first 2 months) sales-wise. Then, Nintendo will need other big hitters/features/whatever to excite people and keep the momentum.

First, it's most likely that NX will be unified platform, that means more games than this gen, also I dont think NX will have short life span like Wii U. Nintendo definitely didn't want to invest in too much games for their worst selling console ever, also I am pretty sure some Wii U projects that were not announced are moved to NX. NX will have much better start with great software lineup than Wii U, almost certain Zelda U port, very possible new 3D Mario game and maybe Pikmin 4 are much better games than Nintendo Land and NSMBU. And at end, Nintendo launch NX with Zelda U port and new 3D Mario means thats most likly we will have another new 3D Zelda (this is actually certain) and another 3D Mario (very posible) in NX life, while Wii U had just on new 3D Zelda and one 3D Mario, also Metroid Prime is very posible for NX.

Regardless how good Nintendo lineup was for Wii U, Nintendo can easily surpass it with NX.

Chances for BC are around 50-50%, nobody can say for sure that NX will have BC and nobody can say for sure that want have.

But Nintendo did said: "I can assure you we’re not building the next version of Wii or Wii U. It’s something unique and different. It’s something where we have to move away from those platforms in order to make it something that will appeal to our consumer base."

So I think that chances for BC are even smaller than 50%.

if your not interested in 70% of nintendos usual lineup you better dont get a nintendo system at all ;)

I doubt you will be more satisfied with the NX then you would be satisfied with the wii u. They wii u has all those games (mario kart, smash, xenoblade) already though, NX might get those till 2018. So I really dont even get the reason people are that excited for the nx. 

If the NX has xbox one/ps4 like power, game development will be even more complex and nintendos software output will decrease even more. And what are you expecting from that system? You will most likely get all those nintendo games that are already on wii u in their next version.

You could ask why are people ever excited for new consoles?

But regarding the NX
-Unified Development across handheld and console (more games, console pokemon potentially). 
-Efficiency in HD game development. (The jump from Wii U to NX will be a much smaller learing curve for Nintendo then Wii to Wii U)
-More Third Pay support (already looking likely but we'll have to wait & see)
-Hopefully lessons learned from the WIi U

How can we define Nintendo's usual line up? I don't recall seeing starfox on Wii and there is no Metroid on Wii U. Mario Galaxy and Mario World 3D are completely different styles. Wii U had no new Zelda game for 3+ years, the NX may have it on day one. I loved my Wii  for the first 3years, loved my gamecube and N64 for their whole durations, so the devil really is in the details.  

Windwaker HD

Hyrule Warriors

Twilight Princess HD

Ocarina of time Virutal Console

Skyward Sword via BC

Minigame in Nintendoland