I'd rather have DQ7 3D remake localized, and an announcement of DQ11´(don't care what platform, except for smartphones i do not want that)

It isn't a payoff, just discounts on royalties + better store positioning + bundling + advertising + dev helping. DQ for 3DS could do big dollars, but Street Fighter on Xbox, looking at SF4, and TR on PS, looking at the last one, would make a lot of money too and that didn't stopped the exclusivity deals.

Whatever the incentive is, it must exceed the opportunity cost. Which is much larger than the incentive vs. opportunity costs of those games you listed. Development costs are cheaper on 3DS, and sales will be higher. Not to mention Nintendo will likely publish the game in the U.S/EU, if it were released on the 3DS. A removal of a 7 dollar platform royalty and financed advertising wouldn't likely make up for higher development costs. 

I'm not saying it necessarily can make it. But both you and I don't have access to this data. I like the TR example because the game sold 50% more on PS3, and X1 has a lower proportional install base compared to PS4 than we had with PS360. And they got it.

And the 3DS entries of DQ didn't sold a lot. A little more than 1M. It isn't that much to avoid a moneyhatting when Sony itself moneyhatted a 8M franchise 2 months ago.

Never played a dragon quest game so it's of no interest to me.

Yes, but the 3DS has a huge Japanese active install base that is 18 times larger than the PS4's and will continue to sell more than PS4's. It just isn't anywhere near comparable. PS3 has a better chance of getting the game, and that might just happen. 

There hasn't been a new single-player DQ released on the 3DS. They were either remakes or an old port of a subscription MMORPG. So that would be like estimating the sales of Final Fantasy XV based on FInal Fantasy VII's and Final Fantasy XIV's performance on the PS4. 

What about XBox fans? Are they excluded from this conversation? Haha...

The game looks pretty cool from what I've seen so far. If I had a PS4, it'd be one of the few I'd get so far.

The install base isn't important if the games are selling just 1M. The DS entries varied between 2 and 5M. It isn't a number that can't be reached by the PS4 that has a higher software sales ratio. And we can't affirm that it will keep selling better than PS4 since it's down YoY and pretty much starting phasing out.

Again stop with the 1M thing. No mainline Dragon Quest (except for the MMORPG - X) sold that low in Japan. Besides Nintendo games and Monster Hunter, Dragon Quest is the best selling video game series in Japan. 

http://gamrconnect.vgchartz.com/thread.php?id=197629&page=1#11

So by the time of a 2016 release, let's guess the PS4 is between 3-5 million Japanese sales. You are asking for a near 80-100% attach ratio for the game on PS4. Meanwhile right NOW the 3DS has 18 million Japanese sales. 

And even with the 3DS' decline, it is outselling the PS4 3:1 at the least in Japan. 

You list has 4 NES games, 2 SNES ones, 1 for PS1 and one for PS2. A 5 year old DQ game for NDS that sold 4M and a 1M game for 3DS.

3DS is outselling the PS4 3:1 in Japan now. We are talking about the future here. 2 years ago people tough PS4 wouldn't outsell 3DS. 1 year ago it was crazy to think it could outsell Wii U + 3DS. Now it looks like it will do it without breaking a sweat. They are exceding expectations and it only takes some big hitters in Japan to get the win there.