I think the constraints imposed by DnD 5e were good for Larian. I bounced hard off of DoS 2 because of the armor implementation and the level scaling gear. BG3 on the other hand had a much smoother gear progression that allowed some gear obtained in the first act to be used for the entire game.
So... I would personally prefer that they make a BG4 or a DLC. However, I never expected them too. I can't remember sources for this, but I recall Sven saying that Larian doesn't do DLC during early access.
In any case, I don't think that they are saying that they would NEVER do BG4, just not next. As implied earlier in this thread, the chaos at Hasbro probably helped them reach this decision (although Sven is too diplomatic to say that outright). Hopefully the project after the next.
