Datamining, Larian's statements. All companions are going to be origins characters, and there are only eight origins characters. Aside from the five we have, there's
Minsc, Helia, and Karlach
. Which itself is deceptively large, because unless Larian changes their plans, we'll be losing a minimum of five of them at the end of Act I ala DOS2.
Depressing if this turns out to be true but not really surprising at all, given that every interaction is cinematic. A poor, poor decision to insist on Origins characters only and a pitiful number of companions at that.
that's the price to pay for going full cinematic and full VOs. cut and limited content tailored for cinematic and voice overs. the best they can do more are probably just like codexes, books, etc. branching dialogues, options, banters, all would have to be sacrificed for cinematics. of course the total number of companions. many would argue quality over quantity. yep. let's wait and look at the quality. and of course those are subjective and arguable as well. you may not like x and think it's bad but someone said it's top notched.