Povhec, I agree, though I am not sure what are the "historicaly Russian areas."

But anyway, "official" language means language of government, school, the language one has to know to work in a given country. Since each Slavic (and in this case Baltic) group has their own language, making any language "official" other than their own is simply not needed. However, this does not mean, as you suggested, that other languages can be recognized. Latvians should feel free to learn Russian, since Russia is among their neighbor states. And vice-versa in Russia on learning, or at least being familiar with, Latvian.