My predictions:

1. Putin won't give up and western countries (EU/USA/NATO) will do nothing at all
2. Ukraine will loose Crimea - the whole bi-land will became a Russian federation, controlled by Yanukovych and/or Putin

Next possible scenarios:

3. Military aggression triggered by Ukraine or Russia leading to war
4. Humanitarian disaster.
5. Ukraine refugees flooding Poland
6. Russia taking over Ukraine

Possible, but rather unlikely:

7. World War III