For those people who are so concerned about the difficulty and brag about being able to solo the game: If the party size becomes 6, I would assume the game would be balanced around this. This means that solo playthroughs would be even more challenging (you are at 1/6th of the strength is is balanced with, rather than just 1/4th). So for you people, this would be a win as you get an extra layer of difficulty and challenge. It is maybe worth thinking about rather than worry about how strangers on the internet play their game and on what difficulty, I think.

I prefer 6 characters in a party too, for several reasons. First, it would make the battles go faster ultimately, due to having more actions. Some fights right now are such a drag and slog already. There would be more agency in a fight and you get more chances to do -something- rather than watch the AI move and think. This is a thing mentioned before by many others too, as an argument against how combat would get even slower.

It also allows for more fun party compositions, with trying less than optimal builds or subclasses that are just fun to play, while not being mechanically that strong. With a larger party size you can experiment more with this without ending with a suboptimal party (this includes going full custom party, with these compositions). Having played the old BG games as well as IWD many times, this is how I keep it interesting and fresh, with strange combinations or to use some underrated/underused kits or classes. If you use the companions, it also allows to use companions you would not use otherwise, be it due to them not fitting party composition, or not liking them as much as ones you always use. Or because you do not use them because the AI beelines for them all the time)

I personally like a slow progression throughout a story, which is not neccesarily based around just exp (at least in BG3, opposed to the older infinity engine games. You get a fixed exp per character where in the old games the exp was divided across the party, so slower levelling). In BG3 the progression is there through gear as well, you have more characters who you need to divde your gear for. It means you cannot just load all your gear unto 1 character and the more people you havce, the slower the gear progresses. This likely also means you have less money and need to think more about your purchases, be it potions, gear or whatever, which makes money and the economy slightly more relevant. Or, if you find a cool magic item you would have to think about who to give it too rather than just giving it to your one fighter, or your one mage (Also, it means more of the magic loot gets used, rather than have so much of it be reduced to vendor-trash or Gale Snacks)
This in effect does affect the difficulty, though not by neccesarily making it easier as you have a group of average/moderatly equiped characters rather than 1 character who has all the good gear loaded unto him/her. Your larger party consists ultimately of more vulnerable characters, which (assuming proper encounter balancing) balances somewhat out with the increased action economy. Also, there will be difficulty sliders (At least that is what I thought) so you can adjust either way.

And having a party of 6 does nothing to prevent me to solo the game either, a person can like both. Sometimes they want a challenge and that accomplishment of a solo run, sometimes they want to just chill and have a party of adventurers with some fun classes that may not be fully combat optimized. No playstyle is right or wrong and they can co-exist.