I don't see that happening. Russia wants the money, and Europe wants the energy. My fearless prediction: America and the EU will come up with some sort of set of sanctions. These sections will be vague, and full of loopholes.
Nothing will change. Putin keeps the Crimea. The natural gas will continue to flow, although there might be a symbolic stoppage for a short while.
And then the EU will realize that the Big Dog on the block is no longer the USA. It's Russia.
I wonder how long until China let's the Norks off the leash, and while we're distracted, they mosey in and take Taiwan without a single shot fired.
Mark