So far, these are the changes taking place during the month of April:
Effective 4/1/18: Pacific Surfliner (contains changes for the new early morning northbound run out of Los Angeles)
Effective 4/7/18: Ethan Allen Express (Saturday's #292 slight adjustment)
Effective 4/29/18: Empire Builder
The Northeast Corridor New York-Washington and Northeast-Virginia timetables that were revised on March 10th should have again been revised around March 25th when the Cardinal was temporarily cut back to Washington and the weekend morning Northeast Regional pair (152 & 153) was temporarily suspended. They weren't, but they might be quietly slipped in well after the fact.
Coming in May, San Joaquin and Crescent timetables will change.