There are zero chances we will not get a Russian/Ukrainian voice over option for NPCs. Metro series had it too, iirc, it's been many years since i played them. It's made for that trailer so as to not confuse new players in to thinking it has no English voice overs.
Splinter Cell: Chaos Theory and Crysis had a great feature that forced enemies and NPC to only speak their native language on high difficulty. So soldiers spoke Spanish, Korean, Chinese or Farsi and in Crysis they only spoke Korean.
If STALKER 2 has such an options would be so cool. Soldiers speaking Ukrainian, Stalkers a mix of Ukrainian, Russian and English, mercs and scientists English and other European languages. That would be massively atmospheric.