O/T Michael Tobis, and some caveats from his comment section:
Some of it is saved, much is merely postponed. Some will cancel vacations and business trips, but the people stuck away from home will ultimately go back and many vacationers and business travelers will still fly at a later date. They may be on flights with higher load factors, they may choose alternate modes of transport, but I'd like to see an estimate of the net emissions permanently avoided.
I hear Europe's high-speed trains are packed, which would presumably result in an overall decrease in emissions, although John Cleese isn't helping. And here's a cool picture of "Yokel Hoop" (read Tobis for the ref.)