In the Swiss format you qualify to Playoffs by going 3-0, 3-1 or 3-2 and you get knocked out if you go 0-3, 1-3 or 2-3. Let's assume the most negative scenario for the West: Eastern teams take the two 3-0 slots and the three 3-1 slots and qualify. We'll give Western teams a bit of a break and let GAM get knocked out 0-3 or 1-3 along with four Western teams. This leaves three Western and three Eastern teams at 2-2. If any Western teams draw each other (about 60%) one is guaranteed top 8. In the other case, East vs West, East vs West and East vs West, some of the best Western teams at the tournament get three opportunities to beat some of the weaker Eastern teams at the tournament. We'll be pessimistic and say each Western team only has around a 15% chance of winning their bo3 at 2-2 against the Eastern team. That's still ~40% (1-0.853) for any Western team to win their match-up.
So yeah, in pretty much the worst case (unless GAM goes 2-2 or better), there's still a ~75% (1-0.4*0.6) chance of a Western team making it into top 8.