After the first of the year, things generally slow down a bit, so there is no telling whether or not you will get the hours you need. I haven't heard any word on whether the UTU conductor's guarantee (for extra list employees) has been extended, or will be eliminated. NS doesn't like paying people to stay home, so if things slow down dramatically I would expect there to be furloughs once they start paying out a lot of guarantee money. If the guarantees are eliminated, they won't care if you only work a handful of days per month.
Considering where you are in the process, you wouldn't be out of their training program much before summer anyway ... and that's if they hired you NOW. So, unless things slow down so much that they cut off all the ACT's (conductor trainees), you will pretty much have a steady income until you are promoted. Over the past few weeks, they have been short of engineers in A'town, so I would expect they are going to send conductors to LET school, which in turn increases their need for conductors. For engineers alone, I know of several who are retiring just after the first of the year, so there will be a need for additional engineers.
On the railroad, seniority is everything. If they offer you a job, and you really want to work for NS, take it NOW ... not later. If you are about to get cut off in Allentown, chase the work to another terminal (such as Harrisburg or NJ) if your seniority allows you to hold a position there. Get qualified wherever you can during your training period. The more places you are qualified, the greater the chances of you being called to fill a spot. Figure out a way to pay the bills if you get furloughed, or are working sporadically once you are promoted. The only way to get past the potential of furlough, is to get the seniority clock ticking.