I don't think so. Basically the stakes are not high enough for someone in either Obama's camp or Putin's to want to press any red button on a nuclear missile. The situation in Ukraine is dangerous but nowhere near a war between the US and Russia.
The likely outcome is a rumbling civil battle - I wouldn't say war - between pro Russian and anti Russian forces within Ukraine. The possible worst case scenarios for this might be:
Putin keeps Crimea but fails to win the eastern cities in Ukraine - pro Russians leave Ukraine to live in Russia. No interference from western powers,only sanctions and strong appeals.
Putin orders tanks into Ukraine and kills many civilians in the attempt to over-run eastern cities. US and Europe and UN condemn. Heavy sanctions against Russia.
Putin breaks agreements and orders air strikes and ground force invasion. US Europe and UN would have to agree on solution - extreme sanctions, withdrawal of diplomats, isolation policy.
Russia is going through rough times at present - economy not good, oppression of free speech and so on - when the economy turns I see better times ahead but Crimea situation still has to be worked out and further deals done between Ukraine, UN and Russia for the future.
I truly hope Putin doesn't go crazy on us but I think the forces for good are too strong for him to do anything totally stupid.