I still think Russia is just posturing at the moment, mostly in an attempt to agitate the eastern Ukraine and, in its aim, get the eastern Ukraine seeking Crimea-like referendums. In Russia's "attempt" to put a halt to supposed unrest in the eastern Ukraine, it's actually creating unrest. This is Russia's goal.
Now, if this fails after whatever Russia deems a sufficient amount of time, then Russia may very well come rolling through the east and south all the way to Transdniestria.
I know a military buildup takes some time, but Russia has had sufficient numbers to invade the Ukraine for a few weeks now, as I understand. If Russia was going to do it, it just seems like it would have done it already, instead of giving Ukraine and NATO more time to prepare. Now, if Russia deems the eastern Ukraine not making enough "progress" towards reintegrating (at least economically and philosophically) with Russia, then I suppose all this changes.