It's kind of lol that the entire political exchanges for the past month can essentially be compared to Russia and NATO standing on opposite sides of a football pitch yelling to each other "if you go on it I'm going on it!!!", quite sad really.
This is very similar to Russo-Georgian conflict over South Ossetia, in so far that Russia does not really have any incentive to invade unless Ukraine will try to take Donbas by force.
There is a major difference though, South Ossetia is an independent state between Georgia and Russia, albeit an independent state that Georgia have claimed as theirs since becoming a sovereign country in the early 90's, and one the west do not recognise but still an independent state and one they have never owned. Invading them was defacto an invasion and Russia were within their international rights to come to the military aid of a neighbour.
Donbass on the other hand is part of Ukraine, it was part of Ukraine when it became a sovereign country in the early 90's and it is still considered part of Ukraine's territory, even by Russia. If Kiev's forces step up their efforts to retake the Donbass region an intervention by Russia would not be legal, and while many would argue that wouldn't stop them it would be a significant break in their modus operandi. As while their actions in Crimea were most certainly not totally lawful they were not entirely unlawful either as it was a very grey area. Donbass would not be a grey area, it would be a simple black and white invasion of another country to support the losing side in a civil war.
So the question is, how feasible it is that Ukraine will try to retake Donbas by force?
Let's be honest, we all know that Russia is supplying the eastern Ukrainians, there isn't even any plausible deniability anymore as the Ukrainian civil war has been going on for seven years now so it's impossible for the eastern Ukrainians to not have run out of bullets or equipment without foreign aid, there simply wasn't enough military hardware/stockpiles in the east to sustain seven years of war and the factories/workshops that would repair the tanks are in the west.
What should have happened over time is that the eastern resistance became weaker over time, but we know that hasn't happened due to the obvious Russian help, but at the same time Kievs forces have both received aid from the west and worked to reactivate their mothballed hardware, this has increased kievs firepower and offensive abilities while the easts has remained static. And of course the east are less likely to use their SAMs against Kievs military planes now, considering what happened last time they were doing it.
So in short, it grows more feasible by the day.