Just got back from the schoolhouse and cancelled classes are just a rumor. They are focusing on the 320 right now as those a/c are coming and they are still short on crews for it. 100-150 more for this year. 250 total/year. Not that this proves anything but I saw the room with the new hire laptops almost stacked to the ceiling. All airbus classes til late may or early june. then summer break (little to no new hire training), and not sure what the break down will be for fall but sounds like majority of the hiring/training in first half of this year.
By far, the growth, and newhires will be coming to BOS. JFK is also probably an option for newhires, at least for now. If you get the 320 your seniority will jump initially but will probably go back down as more and more 190 FO start to side bid over once their seniority can hold a decent line.