Sweepstake time... NEC NYC to Trenton - February (seems to be confirmed on stream). Niddertalbahn - March or April. Ambergate to Chinley etc. - May. Mainz to Koblenz - June or maybe July. This one seemed quite far off, reading between the lines. East Midlands - August or September. Suspect this also a fair way off judging by lack of screenshots etc. Note these are entirely guesswork (other than the first one) and intended purely for a bit of fun.
Steam route will probably be the last one to release of the lot. Skyhook route should release before TSG route according to January roadmap. So, Skyhook route, then TSG, then steam. only Mainz-Koblenz, I don't know where to put.
I think they will all release before the summer holidays as that is when dtg like to do there big summer thing, usually a 3 route bundle that won't be announced until much closer to the time.
Since the skyhook route only had 1 single screenshot, it probably is further off. Niddertalbahn felt more 'complete' although there's some more work to be done such as updating sounds and possibly scenery and whatever tsg wants to implement
In each column, things are listed in the order they are supposed to release at the time of the roadmap. Things can change later on, if a DLC gets delayed for example. This is mostly the case for fixes and patches, as sometimes they move very quickly, while others are delayed to new issues. On Thursday, we will get a new roadmap, so we might know more.