Possible Expansion of Ukraine Conflict to the West?

Link: World War III?

This fascinating and well-researched link concerns a subject you hear whispered about on the periphery of many conversations in Washington DC and many European capitols.  Will the conflict in Ukraine expand in a western direction?  As long as ISIS/ISIL continues to be a priority for military planners, Putin has an opportunity to consolidate his position.
Whether or not he is prepared to start flinging nukes in the direction of Warsaw is another question altogether.  I do not see it to be in Putin's best interest to expand the number of nations already involved in the Ukrainian crisis.  First and foremost one must consider the viability of the current Russian military.  A great deal of hay has been made of recent increases in Russian military spending along with what appears to be legitimate efforts at streamlining and modernization.  But the Russian Army still has many problems to address, the least of which are outdated equipment and troop morale.  It's accurate to say that the Russians have the capability to strategically deliver nuclear warheads to European cities.  But what would the reaction of NATO and the western nations themselves be?
Poland has been one of the few European countries to call out Putin.  It's obvious there is no love lost between Warsaw and Moscow.  But Poland in 2014 is not the Poland of 1939.  Any attack against Polish citizens by Russia would undoubtedly involve a full-scale retaliatory strike from Poland.  The Polish Air Force is large, modern, and well-trained, with a combination of both Russian and U.S.-made equipment. And I have to believe that any attack on a European nation would trigger a response from NATO.  I believe Ukraine is Putin's one free opportunity to swallow geography (Crimea) without military confrontation with the west.
The evolution of Russian involvement in Eastern Ukraine leaves me to question the ability of the regular Russian Army to mobilize and work in concert with the appropriate Air Elements.  Putin has had plenty of time and opportunity provided by a weak response from the United Nations, NATO, Europe and the United States to consolidate his (or his surrogates) hold on eastern Ukraine.  If the only response to the shooting down of a civilian jumbo jet are frowns and more sanctions, certainly the opportunity was there to act decisively and consolidate Russian guerrilla's hold on areas around Luhansk and Donetsk.  But Putin did very little.  Not long after the Malaysian Airlines incident, the ISIS/ISIL dilemma raised its ugly head.  And still no aggressive response from the Russian Army.  I think Putin has lost the initiative and is now searching for a diplomatic way to legitimize his gobbling up of Crimea.  He will be willing to end hostilities in eastern Ukraine in response to recognition of Russian annexation of Crimea.
Actually, I have been very curious what would ensue from a full-scale confrontation between  the regular Ukrainian Army and Russian forces.  Some might surprisingly discover that the Russian bear is still coming out of hibernation.