Zelda become turn-based and DQ becoming real-time are two completely different things. If Zelda was turned based, it would cease to be an adventure game. However, if DQ becomes real-time, it can still be an RPG. The genre isn't changing, just the way you play.
Also, if you need an example of a game changing for the better, then look at Metriod Prime. It changed the way you played, but retianed everything we loved about metriod. I remember all the cynical debates before it debuted, but afterwards, everyone realized that it was quite possibly the best GC game ever.
I believe Square knows what it's doing. This is it's biggest franchise (FF be damned), and there not going to ruin it just to add some "gimm!cky" controls...