Anytime soon? No.

However, if there were a "credible threat" (real or imagined), TSA might start screening passengers on trains as they do at airports. They'd probably screen all passengers at the major stations, and just shut down the smaller ones (not cost effective). TSA would say it's "safer" for passengers at smaller stations to just fly than risk exposure to a possible terrorist threat.

Crazy? Maybe, but this is the same organization who says WATER is such a threat to passengers that it's banned. (Except for 3.4 oz containers in the MAGIC baggie, of course).