"Reaching Vita levels" doesn't mean much when Vita's sales aren't that bad anymore. In fact, the system is the only one demonstrating growth. If anything, the two systems appear to be meeting in a middle ground compared to last year.
PS3 is doing considerably worse despite a more extensive library, and despite having sold considerably less then 3DS LTD. PS4 also isn't doing particularly well for a new console. I don't think I need to even mention the Wii U. Compared to every other console in Japan, 3DS (and Vita) are doing fine.
And finally, don't forget that just a few weeks ago 3DS sold over 60k, driven by Mario Party. Whether it's with software, a price cut, or a long over due redesign of the primary models, sales will (probably) pick up. I wouldn't neccessarily bet on DQXI, but it certainly won't be mobile exclusive:
http://www.siliconera.com/2013/12/26/dragon-quest-xi-wont-smartphones-says-dragon-quest-creator/
