Yeah, 6-10k/week Japan is like, 360 levels for the first half of this gen IIRC and that was ridiculed to hell and back for those sales back then.
As for the 3DS, like the Wii U, it won't do nearly as well as its predecessor, but it'll do OK overall. I'm expecting a ballpark within what the PSP ends up selling, maybe more. As for its longevity I think Nintendo still has to take the situation seriously for the next two or so years, after that, it'll be self-sustaining for the most part like the DS was. NSMB2+XL+turning a profit+eShop simul releases is a great bode of confidence though, on all four key fronts (software, hardware, profitability, digital.)
I don't think the majority of Japanese devs are ready to switch to making smartphone apps either so with the Vita fast becoming a noncontender, that pretty much just leaves 3DS. But I've been wrong before, and would love it if the Vita wasn't doing *as* bad since the smartphone gaming menace needs to be faced down. It's a legitimate form of entertainment that ain't going away, but neither are dedicated handhelds IMO. My worry is that the 3DS and Vita stumbling will keep spooking the keyholders to these companies (shareholders) who may do some hasty things in the name of short-term profitability.