It is my opinion that conflict between Russia and Ukraine will draw in neighboring countries because the war will affect the trade that takes place in the area. This affect on trade will cause neighboring countries to intervene in order to protect their financial interests in the countries of Russia and Ukraine.
Yes, I think if this conflict turns to weaponry against each other, each country will call on supporting countries army's to be involved. This conflict has a chance of having a snowball effect; starting off as something small and then turning into something bigger. It would be unnecessary for this conflict to turn into more than just a conflict.
I think that any time an unstable region erupts with military tensions and wars it will almost always drag in other surrounding nations to it, I think it is inevitable that if the situation turns into a all out war or heavy combat occurs then you will see countries rush in to aid either side.
Although it may be likely that the Ukrainian crisis becomes even worse, other countries will not become involved in a war over this. Most countries will not even become involved militarily because of Russia. If other countries see the crisis as a threat, they will work diplomatically and economically. As we have seen already, Vladmir Putin has talked with other leaders, like Barack Obama and Angela Merkel, to form negotiations. Most countries are not associated with Ukraine enough to risk a costly war.
Russia is not interested in taking over all of Ukraine. Many parts of Ukraine are inhabited by ethnic Russians who still speak Russian, and Moscow would love to assimilate these areas. However, the world at large will not tolerate an all out war, so Russia will only go so far.
Other countries will support one side or the other through economic sanctions, or other indirect methods. No developed country wants to get involved in a war against Russia, so it likely won't escalate into full military assistance against Russia, and from the way the world seems to be reacting to these developments, they won't be fighting alongside Russia either.