Sure you will be able to get back to the TTC (MK).
Even if the MK is already closed, Disney still needs to provide transportation for WDW guest staying the the PR, GF, and CR to return from Epcot....not to mention other WDW guest staying at other resorts who want to visit these resorts at night for dining, etc. Just realize they don't run all night though, typically only 60-90 minutes after parks close, so you need to move with a purpose and not get caught up with some other activity.
There will also be buses taking people back to the PR by bus too, which is right next to the TTC. I didn't mention a bus back to the TTC, since I have no knowledge of this bus line option.