We want to plan a trip to Rome in March 2017, but want to confirm Pope will be there when we go. All websites only show his schedule through the end of 2016. Anyone know when his schedule for the new year is usually released?

The release is very irregular. I've seen times when parts of it were released only weeks in advance. You'll just have to keep checking.

Things like overseas trips are announced a few months in advance, but there is always a chance of last-minute changes with regard to his daily diary because of world event, natural disaster, his state of health etc.

I was going to say that the present Pope is fond of making unscheduled visits so his published programme can never be 100% relied upon.

If you need to book your travel soon and want to take bets on his schedule, you could shoot for the week of Ash Wednesday which is March 1st next year. Normally the Holy Father says a Mass that is open to the public (it was different this year when he said Mass with just the priests designated as 'Missionaries of Mercy' for the jubilee year). Depending on how you schedule your trip, you could shoot for seeing him at the Sunday Angelus at St. Peter's at the beginning or end of your trip, the morning Wednesday audience on Ash Wednesday and/or the usual 5pm Ash Wednesday Mass at Santa Sabina.