Turn based combat is superior in my opinion. One reason is that it is more accurate to the ruleset and breaks less of the system as a whole. However, turn based combat is inherently more difficult to implement in multiplayer, even with few players.
Because I want Baldur's Gate 3 to allow custom built modules and servers that allow at least 50 players each, it would be nice to see the option for custom servers to alternate between a turn based or a live action ruleset. If you remember Pillars of Eternity 2, they released, some time after launch, a very popular turn-based ruleset. I could see the same here, but there's so much that goes into such a decision in terms of balance alone, before you even get to the actual developmental challenges, that it isn't necessarily realistic, but not impossible.
Between the two turn based is the better option, but it leaves some unfortunate possibilities, like keeping the player numbers at 4.