So, after looking at the End of the line trailer a few times. I can guess what the possible gamemode they are adding is going to be like.
One of the possibilities would be a hybrid of Payload, where the cart is constantly moving and Red team needs to try to blow it up before it reaches their base, much like the community made Gamemode "Stop that Tank!"
another possibility would be Red team would start out on the back end of the train, and have to reach the other end to shut it down while Blu team tries to stop them.
there's a lot more possibilities. anyone else got any more?