^Or maybe it hasn't taught them anything useful :)
Basically many developers wanted toolchains that allowed as unified development as possible between PCs and consoles. The 360 has always been the best in this regard, and the PS3 had to catch up, but was always at least in the game.
The Wii has been much more difficult to include in this because of its technical specs and pioneering motion controls.

If next gen the new Nintendo console is treated on par with the other consoles by all parties, it will be probably more because it will be in the same ballpark as the rest from a development point of view - both graphics and control development will probably be more leveled, and not really because the developers will change their ways and fragment/specialize their processes.

@WereKitten: Next gen the three systems will likely be closer to each other specswise than this gen, but the gap between PC and consoles will be bigger, so that may be where the "line" will be drawn.

If we look at last gen, all the platforms (well, maybe with exception of Dreamcast) had good third party support right out of the gate. But due to the popularity of PS2, it was largely dropped from the other systems. So, despite the ease of porting the games from PS2 to GC and XB, it wasn't very popular thing to do.
Sony and M$ try to enter the same game with Nintendo, leading to three platforms that are close to each other specswise, and before any of the three gain dominance, third parties are generous with their games for all the consoles.

On the contrary, I think what this gen has shown us is that third parties will shun a console even if it means it will be financially inconceivable for them to do so (Nintendo Wii) as many Third Parties still are.  There's nothing to say that the next gen won't follow the same pattern of third parties just making games for whatever system they 'want' to make games for instead of what is most financially sound.  Especially if Microsoft continues the practice of paying them large amounts of money up front to develop games for their system or the next Sony system has the best hardware.

@Kenryoku: The third parties that try to keep away from Wii development are the ones that have the biggest gains in high cost of development and blockbuster model.
Because after a certain point of sales you make more profit with the HD consoles than Wii, a huge blockbuster pays off better on HD consoles, it doesn't make sense in short-term to create the blockbuster title for Wii.

If a third party company is able to create a huge blocbuster, it makes more sense for them to make the game for the HD consoles, even if the same game would sell slightly better on Wii.

The higher dev cost is effectively limiting the competition on the HD consoles, benefiting those, who can phase out hundreds of devs and tens of millions on a single game project.

Now, because Wii is having the most 3rd party games, it's obvious that they've effective been shifting.

Even the blockbuster companies can't avoid Wii, since if they don't put out games for it, next gen, the Wii owners don't care about the games from the blockbuster companies. As Activision have said, they invest only to IP:s that they can sell for the next decade, which also means that they can't ignore a platform if they want to keep the IP relevant in the future.

Now, essentially i was talking about what kind of support will the next gen consoles have out of the gate, after one starts to dominate, that's where the 3rd parties start to shift their focus. What happened at the launch of this gen, was that Wii came out with virtually no 3rd party support and PS3 came out with huge support. Because PS3 underperformed in relation to expectations and Wii overperformed, lots of 3rd parties lost lots of money.
What they have learned is, that they can't afford to bet the wrong horse, no matter what they want or don't want.

Also, "Wii".

@Everyone

Third parties avoid Wii because Wii owners desire Nintendo published titles, and Nintendo doesn't do as much to promote 3rd party software. This will not end because Nintendo doesn't want it to. Nintendo games sell better as a result of reduced competition.

Nintendo spent the entire life cycle of the GameCube focusing on promoting, luring and trying to even fund third party games on their system.  And we all know how well that turned out.  Is it any wonder why they are focusing more time on their own games this time?  And last time I checked, they also are focusing on trying to get third party support on the Wii still.  They just aren't begging like they did with the GC.  Now they've just developed a easy to develop for system with tons of options (controller and platform options such as WiiWare or traditional media) and pretty much make third parties the biggest focus in all of their apperances in places like E3 (yes, third parties are part of the 'opening gaming up to new markets' right along with grannies and women).

But most of all, as people have shown many times, over half the best selling games on Wii are from third parties.  So the few who try have shown you actually can make good money on the Wii.  Its the others who need to try.

1. It will be 720p or at the very most 1080p. Nintendo wants a family friendly console, not a graphical powerhouse. I'd be surprised if it was 1080p.

2. It'll be out in November 2011 giving the Wii a solid 5 year run

3. It will be called something like Wii 2 or an entirely unrelated name. I highly doubt Wii HD because that sounds more like Wii upgrade then a brand new console.

4. Will launch with a Mario title or Wii Sports 2 at probably either $229 if they realize that the low price is what gave the wii the edge...or it will be $299 or more if they get greedy and think theres no way they can lose (*cough* Sony)

5. It will probably have really upgraded motion controls that do a lot better job at mimicking your moves. I doubt it will be 3D or like a full body motion control thing.

6. It'll have 3rd party support right away, at least I hope for their sake.

7. Online will be a big part of it. I think theres a 50/50 chance they could charge for online like MS.

I'm not sure online will be that big of a focus for Nintendo it probably will be better and will still be free but nothing like xbox live.

HD is output is certain, 720p native possible (most games on PS360 aren't) with upscailing to 1080p possible

as for controller something comparable with the Wii-mote is likely

and considering the current management I don't really think history will be a good indicator of the next gen

Nintendo's next console will be made of chocolate and will be edible.

I predict the next Nintendo console will have Zelda, Mario, Metroid, Mario Kart and Super Smash Bros. and it will be awesome.