I'm not quite sure how powerful Soldier Boy is, so far he's basically the asshole version of Captain America and if we're "realistic" ( realism in a superhero show

) he couldn't stand up to Homelander, who has Superman level power. So it could be that the Russians abducted him somehow ( maybe with some help from a russian Supe) but i guess we'll see soon as The Boys are headed for Russia.
I think it's a given that we're going to see a big showdown in the season finale - Homelander and allies ( those who are too scared to break away from him) vs. V24 powered Boys and everybody else who has a score to settle with him ( Starlight, Maeve, possibly A-Train) but i can't imagine him being killed off because he is the biggest villain in the show and there's no successor being built up so far.
However the show is so amazing that i'm pretty sure what we'll get will be awesome either way.