The Baltics would. They're fighting for their own land. And if they don't, that's their problem. This is gonna be a lot like Afghanistan. We will destroy their air defense systems along the border, swat their aircraft from the sky and then destroy Russian units in Estonia with by having Estonian ground units point them out.
What if it is not just Estonia? What happens if it is all the Baltics and Poland at the same time? We live in interesting times.
The problem is, does Estonia have enough men in arms to do any good? I think they have spirit and would fight if they thought they had any chance to hold out, but they might all be dead or captured before we could get enough assets into the area to turn the tide. :-(