The game will also change the command battle system, but still be the well known turn-based RPG battle system.
Don't think it'll be such a big departure from what the combat was like before. The one thing that does make me hesitant, however..
The announcement trailer showed very little, but gave an ominous tone with its fiery text, and a voice saying “what is the purpose of light?” Creator Yuji Horii also described the game as “an adult Dragon Quest” during the livestream, and how a decision players or the character makes will change the game dramatically.
For me the appeal in DQ has always been the whimsical nature of the series. That said they weren't childish games. I hope they aren't trying to go full grimdark here, though I don't really expect that they will. We just might get less Sylvandos this time.
The claim that it'll have C&C is also a bit suspect to me. Having meaningful C&C in a game that's over 100h long isn't really a feasible thing, unless they cut down the game length by a lot from what it was in DQ11 (which I'd be fine with, the game was too long).