We're in India but from a very remote and very small state of the North-East. Hence our language Manipuri is not spoken in our current city (Bangalore). It is very rare to hear our language in any other part of India.
My daughter is now 4½ years. During her early days, we did discussed how do we go about talking/teaching English but not let her totally skip our own language. We tried the one person one language method (we both are Manipuris).
However, we realize that she had picked up quite a bit of her own skills with English and even some Kannada/Tamil as she mingles with other kids in pre-school, and friends in the neighborhood.
She also realized that not everyone talks in 'her local' language and so she talks in English to other people (my friends, her mom's friends, etc). She had picked up lots of words, phrases which we have not taught/talked to her 'consciously'.
Btw, kids do not really need to understand 'languages' to be friends, play and have fun. In all fairness, I'd say, continue with your Russian, help him with English and let him pick up on his own. You'll be surprise how much they can learn. Of course, the pre-school teachers are already talking to him in English.
P.S. Don't worry so much about Hindi and other local language. If he speaks English, that will be good anywhere in India.