They probably will when they're on the brink of going out of business. Until then though they'll remain stubborn.

Here is the thing thing though, in order for the used game market to be so inventory heavy, there has to be a lot of people trading games back in. Whose fault is that? Yeah gamestop has cornered the market and made a killing through some questionable practices, but there has to be a whole that let the fox into the hen house. So where was it?

Whoopsie, my mistake, Valhalla/THQ

Ahh actually that mistake makes a lot of sense lol.

Nintendo could certainly benefit from a little more diversification in their library, either internally or being a little more third party friendly. However, I think the amount of effort required for them to get third party parity with Sony and MS, i.e. have a legitimate chance of being the console of choice for single console owners, would be completely counter productive. It would costs them money and would only serve to increase competition with their own franchises. I think they simply need to position their console as a no-brainer for the Nintendo fan and a easy/realistic option for those without allegiance and those looking for a second console.

Also we've seen even with the Wii, even when the install base was huge and development costs were still low, many developers found excuses not to put their best efforts forward and I think it's because many are intimidated by competing with the Nintendo software juggernaut on their own turf.

No, I typed that while I was at work lol. 

If they weren't porting those same games to last gen systems I might agree with you ... 

Of course it will not

Let's see some games that have some years on the market...

AC1 sold about 180,000 copies on it's 7th year. AC2 sold about 259,000 on it's 5th year. CoD4MW sold about 214,000 on it's 7th year. CoDMW2 sold about 322,824 on it's 5th year. All of them on two platforms with an install base of over 160,000,000 or so.

Pretty nice, huh?

Now let's check some Nintendo games with a similar amount of time on the market. First goes Super Smash Bros Brawl... 581,561 sold on it's 5th year and 368,495 sold on it's 6th year. Well, who would've thought that?

It's New Super Mario Bros' turn... 2,175,158 sold on it's 5th year and 564,615 sold on it's 7th year. Also, 228,323 sold on it's 8th year. Gulp.

Now Super Mario Galaxy... 782,439 sold on it's 5th year and 141,487 sold on it's 7th year. Pretty bad, eh.

Let's throw New Super Mario Bros Wii in there... 498,753 sold on it's 5th year. Not too shabby.

What about Mario Kart DS? 3,682,176 on it's 5th birthday and 759,556 on it's 7th. And 220,980 on it's 9th.

Heck, let's check Zelda Twilight Princess, considering Zelda games are not as 'heavy hitters' as those other games... 504,067 on it's 5th year and 212,800 on it's 7th. Hmmm...

Let's check CoDMW3... About 580,000 sold on both platforms on it's 3rd birthday, for a whoping total of 28,000,000 units sold. Surely there's not Nintendo game that can top that!... Unless it's the favourite of the Hardcore Gamer Master Race, Wii Fit Plus, with 1,014,106 sold on it's 3rd birthday.

Now Mario Kart Wii... 1,173,122 sold on it's 5th year. Well yep, I guess I was wrong. And on a more serious note, the only series that I think can compete with Nintendo games in the legs department is Grand Theft Auto.

Miyamoto saying that they started work on their next console means nothing. Sony and MS have also started by now. 

They absolutely DO consult third parties on the designs of their consoles. They didn't get the power right, but it doesn't mean that they don't listen. Source What they don't do is pay for marketing, and bribe for content like Sony/MS, though they did that in the past. 

What is your definition of "third party friendly", because when they unveiled the Wii U, there was a LOT of praise, a LOT of it; even from developers that haven't worked with Nintendo a lot in the past like Crytek, Epic Games, and Irrational. What happened between E3 2011 and Nov. 2012? Is it Iwata's fault that most of them bailed before the console even launched? They sure as heck sounded like they were satisfied at E3.   If third parties hated the Wii U, then why did they all smile and put on a facade for fanboys? In '06 before the Wii launched, several developers called it a "GCN 1.5". That didn't happen with the Wii U. I don't know if it's poor communication or what, but if they don't like something, then they should be upfront about it. It's not like Nintendo can't improve as well (online, eShop restrictions, specs), but I don't see the logic in completely placing them at fault here. 

As for the future, the Wii U will be a bitter pill to swallow. Believe me, they definitely WANT third party support, but whether or not they actually get it remains to be seen.