What if the next DQ is on the 3DS successor? 2016 is when Nintendo will be aiming to launch their next hardware, so it would make sense if they had a huge game lined up for this period.
Well, since everyone is pointing out all the "traditions" associated with DQ, let's point out that DQ never releases near a system's launch. It's quite the opposite, it usually comes out near the end of a consoles life. Which could lend credence to the PS3.