I'd be surprised if Russia and the U.S. really went at it. I lived through the end of the last cold war, and despite all that saber rattling neither country threw a nuke. The current level of cold war will surely continue, or intensify, but I would be surprised if Russia escalated to open warfare.
Additionally, as financial conglomerates overtake nation-states as the world's most powerful entities, the possibility of open war between super powers seems to diminish. Corporations are often transnational, and globalization means damage in one spot could inflict pain in another.