Some form of transportation to TTC will definitely be available until the park is empty.
On 9/1, the 1st party night, the Express Monorail was scheduled to run until 11:30pm, and the Resort Monorail until midnight.
I think the Ferryboat runs until an hour after the end of the party (not 100% positive on that.)
Buses would pick up the slack, and take any stragglers leaving the park after both the monorails and the Ferryboat had shut down.