As for subclass/Patrons, I think they will stick to the PHB for now and introduce others in patches/gift bags. We get loads of variety as a Warlock. A Fiend, Old One, or an Archfey. Add to the type of pact boon, a Tome, powerful familiar or magical bound weapon, loads of room for customisation and role play. Not to mention that the role the Patron will play in-game.
"Will warlock patrons have a large narrative weight in the story?
David: Just like cleric gods and paladin gods, the warlock patron is a variable we know of and can react to. Currently they introduce dialog options and voice-barks. More is possible, but not planned for the EA act".
Source-
Baldur's Gate 3 AMA 2020-03-13 Reddit
