yea I think people on this thread are over reacting, just buying a few weapons, it's 2 billion dollars, what's the big deal, even if it was 5-10 billion so what.
You got no disputes with the US yet, a sanction could be imposed and conditions could be set, but I doubt it will, because it would take another nuke test like event for a sanction, and as for conditions on weapons, as long as you don't use it for US allies, IE Pakistan, you are golden.
Besides, it's a few minor weapons. Even if the sanction did happen, I doubt a few helicopter and a few unmade Tejas will be the difference.
As to Russian response, they won't say anything, on the market place anyone can buy from anyone else, it's not in the Indian constitution that only Russian equipments are to be bought, and it's not like Russians are refused a chance to be chose, it is what it is.