We're visiting Florence, Rome, Naples and Salerno Aug 1-15, 2023. May I know when timetables (especially for high speed trains) will be released?

I was able to book my high speed train trip 3 months in advance last year when I visited.  

One thing to know, in case you don't,  15 August is a bank holiday - Ferragosto. (some business were closed for most of the month in Rome.. wasn't a big deal,..) we flew back that day and were told to make sure you book the ride to the airport days in advance.  Even the train had a different schedule.   I was told it was due to the holiday, so just FYI.

Have fun!!!  

You should be able to book on line a month ahead.