There will still be availability that late in the day.
In June, we had a very late meal at The Wave before heading to MK for the Pulse Vigil with our CM friend. Because we had been seated quickly, we realized we could fit in a ride before park closing. At 9:00p, we found FP availability for HM, BTMRR, Pirates, and many others - booked Pirates and just needed to get there before 10:30. We even had time to ride 7DMT as Standby after Pirates!