Yes and no. After your 3 FP+ are used (once the window opens for the timeframe of your 3rd FP+) you can go to a park kiosk (ONLY, you can't book online or on your phone) and select an additional FP+ (and subsequent, as each window opens up). Those additional FP+ can be in other parks, while the first 3 have to be in the same. So once you use your 3 FP+'s you could hop to a different park, go to a kiosk and try and find availability for another FP+.