I don't think the 3DS fall line up will be an issue. Even if it ONLY has pokemon and the aforementioned Project Mirai and Level 5 games it'll still do huge numbers. I sort of expect Monster Hunter 4 to still be charting through that period and there are enough releases in the summer to give it some huge momentum into fall even if Pokemon has to sustain the boost on it's own.
It's getting Mario Party as well, which did big numbers on the DS. There is also obviously unnannounced stuff that will make an appearance this winter.