Is there any likelihood at all that further npcs might be added in the future? In your estimated opinions?
Very unlikely, I would say. Companions are integrated into the story, and considering the amount of reactivity of BG3 that would mean going through every interaction in the game and coming up with additional scenarios. That could mean work not only companions but other NPCs we interact with.
Than notice that most companions have major areas in the game tied to them. So to keep it on par with the competition, that would mean making changes to the existing maps.
Nothing stops them, of course, from adding something closer to Sir Lora (D:OS2) but I don't know if anyone actually wants that.
As it is, BG3 already has the most robust cast of Larian RPGs. Dwarf are just too heavy to get thrown, and not sexy enough to make into the roster. There were suspicions that planned origins (Helia) were scrapped in favour of Jaheira/Halsin, but after playing the game I suspect it was more of a workload saving move. Minsc, Jaheira, Halsin (didn't try Minthara) seems like less content intensive additions. Even Karlach seems light on content compared to the other origins.