I am waiting to book 4 train tickets from Venice to Rome for beginning of July but I have been checking for a month and no summer schedule yet? I thought you could well inadvance.
Mina, it is normal for Trenitalia to be tardy in posting the summer schedule. Just be patient. Last time we went to Italy in the summer, I was not able to buy our tickets until late May. I even bought one from Rail Europe, thinking they would know the new schedule earlier, but that ticket did not arrive until June 10, just a week before our departure. So stick with Trenitalia and just keep checking.