"Depending on your degree of risk aversion, you might want to consider getting a Russian visa even if it isn't required. Doing so would make things easier and more pleasant if delays or cancellations force you to spend the night in Moscow. You may need a visa anyway because you are changing terminals at SVO." From previous poster.

Even though you are changing terminals in SVO, you will NOT need a visa, they are interconnected. You will go through security but not passport control anywhere.