if by change to BG1/2 combat system you mean real time w pause, then that is never gonna happen.
Larian was chosen by WotC specifically due to their experience with turn-based combat systems (among other things), and they have been up front about this for long.
if you are referring to characters only attacking once, then that was the same in BG1 and BG 2, and most other crpg's in the low levels, it allows for progression.
level 4, which is all we have in EA is still fairly low level, but by DnD 5e rules fighters and rangers (among others) get a second attack at 5th level, around the same time spellcasters get 3rd level spells, which are some of the most fun and powerful ones (untill 5th or 6th level spells), like fireball.
Rogues already in a bit of a weird place atm in BG3, so i am looking forward to what they will do with them.
