I first and foremost hope that we get a variety of characters in terms of race, age, background and aesthetics, not just a lineup for the Rivellon edition of The Bachelor.
Secondly I hope for companions that match the darker theme that was hinted at in the trailer. Characters who are grittier, more complex and flawed and not fluffy Disney princesses.
The Red Prince was in theory pretty dark. Slaver, demon summoner,...
But Larian can't write serious characters. And when they continue BG3s trend of just having waifus I doubt that there will be any dark character.