Is Russia responsible for separatists in the Ukraine though? Heard the transcript of the rebel's communications following the incident this morning. If it is indeed real then they've put their foot in it.
If there are repercussions though then Ukraine will be wiped off the map. Risk of nuclear war is too great and conflicts would be isolated to Russian territories and points of interest like the Crimea and Ossetia. I just expect a lot of posturing and some trade embargoes.
Then again, the final triggers for WW1 was an assassination and WW2 was a false flag operation.