The patio usually had open spots. Esp if you're going from a 9pm Illuminations, back to the hotel & then there around 10:30/11pm I'd say you'll be fine.
I THINK the patio might close up earlier, but I'm not sure. And in all honesty, I had Fri/Sat's off and we only had trouble getting inside the first few weeks it was open! Then the hype died down, if you want to get inside, they'll give you a pager, and you can sit outside & enjoy the same menu while you wait!