Question regarding region-locked copies and DLC (PL/RUS)

Hey,
I've just been informed that if I'd purchase the game in my home region (Poland), I'll be locked out of the English language version and forced to deal with the localization, both text and audio. Tragic and damn unfair, but I get where they're coming from (the game is sold cheaper here). No worries I thought, I'll just get my copy from GMG and pay a bit more, to enjoy the ENG version.

My question is for people with experience of dealing with region locked EA games in the past (Battlefield 4 had this issue, AFAIK) - if I'd buy a "Global" base game key, what would happen with future DLC releases (map packs and whatnot) in terms of compatibility? Would I have to also purchase "global" keys for those as well, and are DLC region locked at all? 

The above is quite important for me, as while I can take the financial hit of having to buy the game for a higher price than I normally should, if it applies to all future DLC as well I might have to re-consider the purchase altogether.

EDIT:

One more thing, please confirm for me that if I'd get a key in Poland, I'll be forced to only use Polish audio, and English audio will be locked out. I've seen a post contradicting this on some forums, but no official/realible source.