in my opinion China is very unlikely to ever impose sanctions on any big trading partner as China's economy is particularly geared around exports (hence the artificially pegged weak Yuan / Renminbi) - plus they are a huge importer of natural resources (eg iron ore, coal) - they would hurt themselves the most.

I believe that serious US/Euro sanctions on Russia actually have a more severe and longer term impact on Russia's economy than Russia would admit to. Please note that I am not commenting on the fairness of sanctions or lack thereof, merely on their effect. And I am not talking about restricting travel to Putin's inner circle, but level 3 or higher level of genuine economic sanctions. I believe this genuinely worries Russia's leaders, particlar with regards to longer term economic growth and development. If implemented, such sanctions would eventually affect ordinary people, though emotions of patriotism would for some time cloud the consequences. Such sanctions would hurt some European countries too; especially those that would have high level export opportunities with a growing Russian economy. In particular this is the case with Germany, whose export of high value and high tech machinery has been flourishing with Russian companies over the last years (automotive is one example). The issue of gas reliance from Russia gives Russia currently an advantangeous lever (the dependence on russian gas ranging from 30% in some countries to 100% in others within the EU). If Russia were to withhold supply, it would hurt Europe in the short term; but I am convinced that Europe as a unit would find alternate solutions to the energy supply and thus in the longer terrm Russia would be without one very valuable customer for their abundance of gas. As for the US, they have the least to lose with sanctions as their manufacturing industry is to a lesser degree reliant on exports (and in particular exports to Russia).

In my mind Russia and some European countries would be the real loosers if severe sanctions were implemented.