For the record if this thread exists at all is precisely because both Swen on twitter some time ago and another Larian guy yesterday on reddit said explicitly that while this is what they are going for now, a 4-men party is NOT set in stone yet.
I admire your optimism.
I'm not optimist at all. I just think it's worth trying to argue for it because it would make the game better.
And because "Let's make an argument against it because the devs are PROBABLY against it anyway" is an incredibly dumb way to approach it, regardless.
I argue what's favorable to me, not to align my opinion with/against what Larian does as a ideological stance.
Realistically? I fully expect this to end like with the armor system, the botched progression system and the terrible itemization in DOS 2: with Swen sticking to his guns no matter what,, falling short of the design goal, making the game slightly worse for it, and MAYBE being willing to admit it was a mistake only one or two years later.
