We don't know what kind of origin they'll have in the movie. So far, there's no indication of a High Evolutionary being in the movie. And as for their ethnicity being Eastern European, Roma, British or whatever, I just hope it "agrees" with the names they're ultimately given. If they stick with "Maximoff," I don't think most audiences are going to buy "Wanda and Pietro Maximoff" as someone who grew up in Liverpool or Yorkshire. Stuttgart, maybe, or Prague, Bucharest, or Moscow.