That’s probably a long weekend in Italy, which is usually synonymous for railway engineering works. So there is an uncertainty in the planner. On the other hand, Italy can be a bit late in updating schedules. So  just wait a couple of weeks to reserve. Trains might show up eventually. Trains are hourly and don’t sell out fast, a couple of days before departure there’s usually still good availability.

If nothing shows, best prepare for a bit of a longer journey. But it will cost you less, or even nothing, in seat reservations anyway.

Yes there are works on the high speed line, the timetable is not published yet.