Maybe it's just bluster on their part, but if so they'll look making an unnecessary veto threat then backing down when Russia supports the rest of the Security Council. Russia now has strong reason to do so, since the economic benefits of Iran getting nuclear energy fuel processed there could be as great as selling Iran nuclear weapons technology, with far less risk.

No, on a host of issues, the rapidly increasing economic and diplomatic influence of China is far more critical than Russias. Both countries, however, recognize that for either to gain the long coveted global position America enjoys America must first be removed from it. Most people seem to take the attitude that America has too much influence and the world needs to reduce that to have a partnership of equals. Thing is, the world has never done that; attempts to do so result in a global power vacuum someone always fills. Russia and China both hope to be the ones to do that, but China is in a far better position, largely thanks to our aid and the collapse of Russia with the Soviets fall. It's more likely they'll continue to work together against the US than oppose each other in the short term; they can always pull what Hitler did with the von Ribbentrop Pact, but in the interim they're increasingly presenting a united front, and increasingly getting global support:

http://english.pravda.ru/world/20/91/366/15273_alliance.html

http://www.heritage.org/Research/RussiaandEurasia/BG1459.cfm