I saw an article on Nintendo Soup about a job listing for the next Dragon Quest. Talks about looking for action planners for battle scenes.
My reading of the article didn't convince me that the next game will have an action combat system, more that they're looking for people to make the games feel more dynamic with battle effects, angles, etc. I think Nintendo Soup is kinda sketchy, they seem to take a scattershot approach to news there can sometimes be some logical leaps.
I don't think that main DQ games will ever have an action combat system.
On that note, where's Heroes 3?