Nothing. 3DS has hit the saturation mark.

it seems they are coming into saturation point. the DS trade would be a good option. Price drop as well.
have new bundles like DQVIII and DQVII would help maintain or increase a bit more on hw sales.

I think the 3DS has reached its peak over there. It sells more than 30k per week, sure, but no mayor release will make the sales grows like when Pokemon/Youkai Watch/Monster Hunter came out. Unless Nintendo gets another big new IP like Splatoon, or manages to get some big 3rd party title (a new main Dragon Quest, per example), and even then, the growth won't be really that impressive.

Yep', pretty much this. Now it's time to sell the last bags of 3DS, and think about the future.

A huge New 3ds exclusive. Something like Pokemon, Monster Hunter or Youkai Watch but I can't see Gamefreak, Capcom or Level 5 doing that.