They have already cut the service. I used to, sometimes, take the ACES down on Sunday, the last day it runs. I would then make a circuitous return via Philly, and Trenton on NJ Transit. However, they stopped running a Sunday southbound ACES train, even though it is still listed on the printed schedule.
There wasn't much business on the train and I will not be surprised if they stop the service. I remember the fiirst time they had sevice, back in the 80's, and it ran everyday, not just on Fri-Sun as does the ACES train. The train is so much more comfortable than a bus, so I would use it, if available.
Ned in NYC