So the current batch of rumors seem to be this:
12 is early in development but they're not getting rid of turn based combat
SE decided that westerners didn't like how tedious the game (DQ 11) was to grind
Traditional menu system is "gone" but not really, the menu system will now appear around characters at their specific turn.
You won't use directional buttons to navigate towards things like attack, defend, run away, but now press specific face buttons(I.e. Circle, X, Square) to execute default moves
Directional buttons will be battle commands as well
When you open a sub menu like Magic and need to select specific abilities then directional buttons will work
Party formation may play a bigger role than previous, specific layout formations are intended to grant you specific buffs and party wide abilities(i.e. like you're lower level and want to take on a much higher level enemy so you make a glass cannon formation and see if you can blast it down before it can kill you, or turtle and go ultra defense and slowly chip away and heal)
Square wants a risk vs reward system since many western players like Dark Souls, so higher level world boss enemies may appear in zones
Battles will now have a seamless start and begin when you bump into an enemy, so no loading or screen wipes
The Pep Powers may make a return but as a separate managed resource that the player can utilize at will rather than at random, basically a different and seperate version of MP.
They're taking inspiration from game of thrones because the main bad guy is supposed to be a handsome version of The Night King, so an undead plague and corruption is expected to be the big bad
Art style may not deviate much, but they're apparently aware that westerners think everyone from DQ is from Dragonball Z
I dunno it's not sounding too bad if any of these things pan out.