At this point, I think Nintendo has done everything, especially with all of these 3DS models, like the 2DS and N3DS.

2DS, fresh new IPs and huge names that always give boosts like mainline Pokemon, Monster Hunter and Yokai Watch.

And a price drop if they feel like it.

A Much more successful new IP, just like Splatoon.
Since people who love pokemon, MH, Mario, YW, AC and etc, have already owned a 3DS. Sooooo, nintendo should attract consumers who are not interested in any of them/ any of the current games on the 3DS

EDIT: I basically just said what you said in that paragraph! So yeah, i agree with you on that =D 

Ice Climbers Uprising

The release of a big IP not yet on 3ds might attract some new players and give it a boost. But most important franchises have already had releases on 3ds. Of course games like Pokemon can still give a boost but not like earlier. Also, 2DS would sell some units but it doesn't seem like they will release it over there,

But as you said, its still outselling everything else with ease

3DS is just saturated there. That is okay though, it is still selling pretty well for a saturated platform.

They're already on it, these might possibly improve sales a tad by targeting the japanese female audience.

link: http://www.nintendo.co.jp/nintendo_girls/index.html 

Aren't Japan sales about 30k weekly?

No, not really, unless they have some sure fire system mover up their sleeves which from the looks of it is not the case, the best the system can do is coast on being the best selling hardware in Japan and Nintendo prepare for the next handheld successor.

Personally, I would have one or two 'New 3DS' exclusives in the pipeline that might move units, doesn't have to be another Pokemon entry but something that get a few more people to trade in there original model 3DS games and buy a brand spanking 'New' one.

But all indications are that much like the DSi, before it, Nintendo won't really use the 'New' hardware to its potential and will save up some of the potential ideas/features under the hood outside of Amiibo integration for the next device, which may or may not be the NX but is most likely going to drop in 2016 or 2017.

Nothing. Time to release in a year the NX handheld.