Christmas Day travel -> "It depends" like others have said.
The airlines pull-down their schedule for a lot of late night Christmas eve and Christmas morning flights in certain destinations, traditional business destinations and small markets.
On the other hand, demand to leisure destinations on Christmas day is typically quite strong.
Christmas morning is typically busier than one might think for two reasons:
1) People who couldn't fly out earlier since they have to work Christmas eve (retail industry)
2) Bargain-hunters, typically much cheaper than the days prior
3) Leisure / vacation trips (e.g. NYC - Florida, Ski markets, etc.)
That said, it usually drops off by midday.
I would think that GM's on SFO-CVG should get upgraded quite easily on Christmas day. The DM road warriors are all comfortably at home opening their presents under the tree, enjoying their time off after a long year of slogging around the world.