At 3, sorry for that, but then I just repeat, that means that 3rd parties have it all wrong, horribly wrong. You talk about the R&D into making new tools, but the ones for Gamecube/PS2/Xbox were good enough, all you needed was to slightly improve them at little cost to make up for the slight increase in power and motion controls. Best part is you could then have smaller teams making more games on the wii, and so more money. Easy.
Also, you must realise that just because you, as a developper, want to use new intersting tools to do new things, you shouldn't assume that people, as gamers, will like it automatically.
Going on, it's not Nintendo that needs 3rd parties, but 3rd parties that need Nintendo. On all Nintendo consoles, as well as Sega ones, the idea was for the 1st party to make the hardware sell, and so allow 3rd parties to have a big install base to sell their games. This changed with the PS1 because Sony wasn't a video game company, but a technology company, and continued with Microsoft for the same reasons. True, Nintendo needs 3rd parties to have an overall good library of games, but not as much as you're implying at all.
As for the home/TV experience you mention, it only makes sense if Nintendo wants to move away from just Video games. Otherwise, it's useless. Games won't get better thanks to apps.
Unfortunately, as you mention, Nintendo seems to be heading in this direction, as much as that's a terrible idea, so I can only argue as to waht they should do and not what they're going to do. It just shows that Nintendo can be a very stupid company.
I have to disagree with you. Nintendo needs 3rd parties more than they need Nintendo.
3rd parties only need a vibrant and wide userbase. With PS360/PC they have that. In fact, that base is larger than the Wii and additionally all share a very similar set of capabilities allowing far easier cross platform development by a single team.
Wii requires a different set of tools and a different dev team just for itself. You can't use gamecube tools as those largely didn't exist or were based on PS2; which is FAR lower in tech than Wii. This is why Wii gets tons of crappy games when we all know they could look and be so much better. Devs have been utilizing slightly improved PS2 based engines to make Wii games.
Nintendo makes hardware and software. They want they hardware to sell in order to sell their software. They know the best way to keep hardware selling is to have a string and diverse library selection. Wii was gaining this in 2007/2008. Then all hopes of even better selection with big 3rd party names vanished and since then all we've had to look forward to were largly 1st party games. With that you have a rapidly slowing sales of Wii systems. Its not dead, but its not even leading either.
Nintendo will focus on a far more similar base with special enhancements to ensure 3rd parties at worst can port the same game over and at best can add unique features to push Nintendo hardware as an almost unique experience.