The team also have a lot of time to plan virtual queueing systems that will reduce time spent in potentially rainy physical queues and increase time spent in covered additional spend areas (Mt Doom Fondues, etc.).
It's not like they can't also devise methods of cover for extended queues on top of that. There's a myriad of ways Universal can minimise the impact our weather has on the Park as a whole and I'm confident they'll do just that.