Been saying this for months. Their future is on mobile and pc. Excellent move and as we can see the market approves. If their next consoles don't reverse the decline you can bet your bottom dollar they will go this route. And they may very well live on forever if they do.

NeDa is going to develop these games. Nintendo still make games for their own hardware.

It's perfectly possible to do both things.

They will be jointly developed. Most likely Nintendo will design the core gameplay to ensure good quality and then DeNA will be responsible for maintaining the content back end of it (ie: daily updates, leaderboards, online play, microtransactions, new DLC content, etc.). 

They'll probably supervise these things, but they already have studios for that (Nintendo SPD).

Well apparently they don't, or at least not to the scale to satiate the smartphone market. If they did they wouldn't need DeNA. 

Nintendo SPD will supervise NeDa, I'm sure of it.

I don't see subsidiaries like Retro Studios or Intelligent Systems making mobile games anytime soon.

They could I suppose though I don't think they really need to. 

I mean even if you look at one Nintendo game like Nintendo Land ... that's like 12-15 smartphone games worth of work, lol. And that's only one game. And really some of those Nintendo Land mini-games are far deeper than many smartphone titles. 

A medium sized team at Nintendo could easily assemble and pump out the core engine/gameplay/art for 10-15 yearly smartphone releases and then DeNA could be responsible for the "upkeep" of those games over time. 

I could see the smartphone sector also being where new Nintendo designers cut their teeth in the company before moving on up to full blown console/handheld development, it could even be where big-wig Nintendo employees maybe moonlight after finishing a big project? 

Just spend 2 years of your life working on some massive Zelda console game? Hey why not blow off some steam and make some weird, low-risk, Captain Falcon action game or something for iOS. I could see that being a fun little side/vacation style project for Nintendo designers now and again. 

I guess one positive here is we could see a lot of Nintendo characters and IP return that we haven't seen in a long time since development costs are so low, there's no risk to making say a Captain Falcon game or a Doc Lewis game (lol) or a new Duck Hunt or a new Ice Climbers. 

 I guess, Sonic Team made Sonic Runners  while they're making the new Sonic game after all.

I'm pretty sure Nintendo would be developing those games.

I almost regret selling my stock early Wii days when it was at it's high...almost.