With Nitnendo so adament that they were NOT going to get into the phone game business, why the partnership with DeNA? Well there have been 2 reasons that have had the most speculation.

1: Nintendo realized they could make a practically effortless fortune making games / emulating games to phones.

True, but why would this make Iwata change his mind so quickly about whether to get into that sector of business in the first place? He could have just as easily eased it into realization and no one may have ever been the wiser.

2: This will allow for an infrastructure to stream video games from handhelds to home console (tablet, phone, ect, ect), making the fusion a realized product.

I don't really see this due to the fact that this would be SOLELY dependant on an online infrastructure Nintendo hasn't even embraced. How are they going to go from couch coop and no voice chat to an ENTIRELY internet streamed family of hardware. No, this is not going to be the purpose of DeNA at all, I can almost guarantee it. 

So what do I think the major priority of DeNA will be?

Drum roll please!

Miiverse 2.0. I think they are going to start a complete Nintendo community (like the current Miiverse) but to a level no one could ever dream. You will be able to stream videos to the new Miiverse, you will be able to post review and gameplay videos with no restraints (though there will be no ad revenue for either party), There will be a fan section where you can post fan videogame music videos, there will be game community sections where people can see worldwide rankings (game specific) as well as most popular pictures and videos, you can get game updates (DLC releases, patches) notifications straight to your phone and email, maybe member specific sneek peaks at game releases, ect.

Basically, they aren't going to unite consoles and games per se, but the Nintendo communty as a whole.

What do you think?

I don't believe Iwata ever said they would never enter the mobile market, more like they would never port their console/handheld games over and if they did enter it would be as a way to promote their dedicated hardware without devaluing their ip and not as a way to make a quick buck.

And they still said that when the announcement got made. I don't think they will port any game to mobile, maybe not even games from old consoles since they can still sell them at a higher price in the eShop.

In other words, I'm interested what this will bring, as it will certainly be something new

Like they said, a way to promote and sell their dedicated hardware and software. DeNA is also helping with the membership program which Iwata hinted could involve the more games u purchase, the cheaper they get or offer a referral program. I could see something like this.

Let's say u download the Pokémon Card Game on ur smart device, now u get 5% off the digital version of Pokémon Z. U also invite ur friends on Facebook to play, 10 of them download it, now u get an additional 20% off.

Now Pokémon Z only costs $30 instead of $40. This is good for consumers because u get discounts on games without having to spend a dime. It's also good for Nintendo because it increases their potential audience and increases their digital sales which have a higher profit margin than retail even when factoring these discounts. Nintendo makes more money from selling a $30 digital copy than a $40 retail copy.

Your theory sounds interesting.  But what I gather from what they laid out, it's definitely going to also involve mobile games in some form.  Just not the "free-mium" games that DeNa is currently known for.  That's what Iwata is basically against when it comes to mobile gaming:

"The agreement is as follows:

• Joint development and operation of gaming applications for smart devices using Nintendo’s intellectual property, including its characters

• Joint development of a new multi-device membership service that will span PCs, smartphones, tablets, Nintendo video games systems. The service is expected to launch in fall 2015

• Nintendo will acquire 10 percent of DeNA’s issued shares for JPY 22 billion (US$181 million) while DeNA will acquire 1.24 percent of Nintendo’s issued shares for the same price

Update

During the press conference Iwata and Moriyasu revealed that this deal had been in the works since last summer. With the partnership announced, they confirmed that consumers can expect games to appear by the end of this year.

The format of the games are a big question mark. DeNA has monetized many games by making them free to download, but then requiring in-game purchases to fully experience the game. That method is something which Iwata does not support. When asked how he would reconcile his views with DeNA’s tried-and-true method of generating revenue, he affirmed that he had not changed his mind about the so-called “gatcha” method. That suggests the companies are going to need to get creative to make this endeavour profitable."

https://www.techinasia.com/nintendo-dena-alliance/

“If I was to take responsibility for the company for just the next one or two years, and if I was not concerned about the long-term future of Nintendo at all, it might make sense for us to provide our important franchises for other platforms, and then we might be able to gain some short-term profit,” he said.

“However, I’m really responsible for the long-term future of Nintendo as well, so I would never think about providing our precious resources for other platforms at all.” - Iwata

http://www.idownloadblog.com/2013/08/10/nintendo-pres-on-mario/

This pretty much says that they would never put their franchises on other platforms, point blank period. Though this is just a translation, and I often do not take these as concrete proof of the speakers actual meaning.

Agreed. I don't believe they would waste the time and resources to develop a partnership over something small and fleeting (like somethimg as simple as a new way to look up your club Nintendo account. Whatever it is it's gonna be big.

creating Miiverse app too would be awesome. Nintendo's own social network and easier to access and post anything fans would like to. easier to spread Nintendo news and updates. it is possible.

Nintendo didn't buy DeNA. They just bought some stock in the company.

True, will update.