i dont think its fair to say Ubisoft snubbed their nose at the Wii U. They supported the system far longer than it was reasonable to do so.

Much like the Wii, Wii U, Kinect, and PSVR, I think Ubisoft will be there at launch, just in case things go well.

Some are, some are not. It will boil down to the success of the NX and the architecture of the machine. Companies that supported Nintendo handhelds will be there for the Fusion, now that it will become the only 9th gen dedicated handheld console. Western companies and big AAA eastern games will come to the NX if the hardware sells well and if it's easy to port old and current games. With that said, I doubt some companies will ever come to a Nintendo device, like T2.

Nintendo make Hardware for their game, with unique interface or something.
It might be able to be a little better, but never better than Sony and MS, who make Hardware as platform.

It's nothing personal, it's strictly business.
In other words, if third party's can make money on nx, then they will be there

These are not fan-boys running these companies that catch feelings if they can make money they will be there.

I think it's a bit easy to just blame the bad sales for the bad 3rd party support. There is a lot more to it. Look at what Sony did with the PS4. They've built their system with 3rd parties in mind, they invited them into the development and asked for feedback and what developers want and need. They spend significant time and money to support indies and 3rd party. The result is a powerful system that's easy to develop for and a welcoming attitude from Sony.
The PS4's software support is not just because it sells well, more like it sells well because of the software support and a well thought out system.

If Nintendo hasn't already started a year ago building 3rd party relationships for NX it may as well fail like the Wii U. But something tells me Nintendo will yet again build a console that's only good for them and just hope 3rd parties will like it.

I disagree with the op because third parties go where the money is at. Imagine fi third party games on NX sold 1-2m that's money that third parties would be interested in.

Let's not forget about the 3DS, though. This console actually has pretty decent third party support in spite of the massive dominance of smartphones. Most of these are Japanese devs, but I think the 3DS shows Nintendo a roadmap that they should follow to win back 3rd parties for the NX. The low-hanging fruit that they need to win over first are companies like Capcom and Square Enix as there is already a good relationship there.

Getting console staples like FIFA, Madden and Minecraft also shouldn't be too difficult since they are on just about every platform under the sun. It's going to be a lot tougher for Nintendo to win over devs like Naughty Dog and Bungie because I don't think that there is an existing relationship there, but if the NX picks up momentum then it is absolutely possible.

Regardless, though, Nintendo needs to be proactive about getting back 3rd party support. In all likelihood, the NX won't be as dominant as the SNES or 3DS where Nintendo could just sit back and wait for 3rd parties to come. They are going to have to go out and secure this support the same way that Sony and Microsoft does. It won't make the NX successful on its own but securing 3rd parties is one piece of the puzzle and Nintendo needs the NX to be firing on all cylinders.

If Nintendo can shift units and make the kind of system devs want then 3rd parties come. There's no real bad blood except for maybe rockstar north. I heard they had a bad break up during n64. 

I think it's possible for Ninten to make amends with 3rd parties. They just need to make a more friendly and successful console for 3rd parties, and get into negotiations with them. If they can do that, I think 3rd parties can come back to a Ninten console.