Looking back at BG and other D&D games that had 6 in the party I actually felt always presed to have 1 mage, 1 thief and 1 cleric - which are ironically the 3 classes I'm least interested in. Why did I felt pressed to have them? Because the developer knew I have the space for them and knew that to feel special each class had to shine in its element forcing me to min-max.
So far with BG3 I didn't have this feeling. My ranger can open locks and disarm traps. With a paladin or a bard in the party they could probably heal enough to help worst cases, while actually the party would be deadly enough to not care - or there is at least a druid to replace the cleric. Bard or warlock could also be there to replace the wizard or I could go with a eldrich knight? In any case Larian can't expect a party of 4 to cover all bases so they have to give you more options to handle each situation - and that's what I've seen so far. To me the argument that 4 means tank, healer, dps and mage completely min-maxed isn't necessarily true for a game and I see it not being the case for BG3.
Still I have not played through the entire EA so I don't know if the Act I has the same (horrible) ending that DOS2 had which forced you to commit to a single party - that's something I'm completely against. I hated it in DOS2 and definitely don't want to see these kinds of artifical story based party reductions.
Besides that, I don't mind if the party size is increased, though I think it would just end up the same way BG1-2 and Icewind Dale ended up - basic 1 melee, wizard, thief and cleric + whoever you actually really like.