zaidan

Georgia and Moldova are more likely to be invaded, as there are already possible justifications of this move by Russia (separatist territories, a common rhetoric used by the Putin government, part of the so called Karaganov doctrine of Russian-ethnic people protection and interventions). Armenia and Kazakhstan are less likely to be invaded, considering Armenia is very close to Russia (although the countries have distanced themselves a bit in the context of the most recent Nagorno-Karabakh conflict) and Kazakhstan is in another regional context.

Although it is not highly likely, it may happen if Russia is able to advance and secure a position.

I believe this could only happen if Russia sees a chance of seizing the territory and secure a position advancement, although it is not highly likely.