In Gematsu's report of the tease for the game, they have a translation of the text of the magazine, and it gives a vital clue to finding out the identity of the series of the mysterious game:
"Next to Mario, who else can give 3DS and Wii U a boost?"
http://gematsu.com/2015/03/famitsu-dswii-teases-big-new-title-next-month#rEAsGlXWOdJt2MYJ.99
Sure anyone, can give a boost to the consoles, but if they are mentioning that as a clue, then it means, it must be a big boost, and after going through sales since the Wii U release, this is what I could find, as the 3 biggest boosts for the consoles.
Wii U:
1. The release of the super value bundles - 2k to 39k - 1,323%
2. Release of Pikmin 3 - 7k to 21k - 183%
3. Release of DQX - 10k to 20k - 108%
3DS:
- Monster Hunter 4
- Yokai Watch 2
- Pokemon X & Y
Dragon Quest VII followed Pokemon closely for the 3rd spot.
So Dragon Quest it is?
COMG guide to points: 1 point = Raging. 2 points = Beasting. 3 points = Tearing it up. 4 points = Berzerk. 7 points = Rampage. 12 points = Burst. 15 points = god mode. 20+ points = DIVIDING BY ZERO!!! 40+ points = Youkai (originally Pokemon).
-1 = Negabeasting. -5= NegaRampage. -10 = NegaBurst
