Ehhh I think the effects of the sanctions are overstated. Look at a long term view of the Russian stock market. (5 years)
http://www.bloomberg.com/quote/INDEXCF:IND/chartYeah this crisis hurt Russia but not that much, these levels aren't unprecedented nor is the volatility that extreme.
To actually influence Moscow large parts of Europe would have to be on board, critically Germany. But how willing is Germany to play ball with the U.S. especially with Merkel's phone being tapped by the NSA? Why would Germany want to destroy relations with the most powerful country in the region? To help out an ally that is spying on you? What type of domestic chaos would ensue with people freezing to death in the winter?
Yeah the EU has slapped sanctions on a few oligarchs but no one is even considering touching Rosneft. And even if they did, as much as Russia would like income from oil sales Putin always has the option of increasing government involvement in the economy to create a more command oriented 'wartime economy'. Oil and Gas is only something like 3% of Russias GDP. The benefits of being the largest country in the world, being an oil and grain exporter, is that Russia could be fine without trade. They have a trade surplus, they have food, oil and gas, natural resources and sophisticated technology. They are self-sufficient. Europe is not.