My alternate history for Poland uses a few key points of divergence:
- without Gorbachev and glasnost, Poland doesn't follow suit, keeps pressure on Solidarity and reformists. Soviets take a harder line which the Church buys and does not intervene
- the assassination of Lech Walesa
- widespread protest and unrest
- elections are held but the results are clearly manipulated and Communists remain in most positions of power
- the Wall still comes down in '89, if anything, these events spur it along
- Poland is therefore adjacent to a NATO power as Germany reunifies
- Eventually, a nationwide strike leads to the Soviets reluctantly supporting the Polish government with their troops
- kinda goes from there
The only real issue I've had with this timeline is stretching out the last stages for 5+ years. Frankly, on this timeline, I'd expect the collapse of Poland or final intervention no later than 1992 or '93.