There will be normal park closing bus service for awhile once the park closes for regular guests - non-DAH guests need to get out/back to their resort just as any night.
At some point during DAH they transition to a more limited bus system that will service those leaving DAH. Depending on the resort, bus routes may be combined with other resorts in a non-traditional manner (given the limited number of guests).
Bus service is the only way DAH resort guests (other than CR/BLT) have to get back to their resorts. Monorail and resort launches won’t be running. The ferry will be running.
The above was the setup for the 2017 DAH dates and will presumably be the same for 2018 (although we’ll need to wait and see for sure).
But regardless, you’ll have an option for getting back to your resort, no matter what.
Hope that helps!