So, perhaps this isn't a surprise, but a nice bit of teasing.
It looks like Overwatch might be celebrating the Holidays with an event, much like its Summer games and Halloween ones. This comes from datamining of the latest patch in the PTR done by Reddit user Venxa. They found a ton of audio files, and one in particular seems to give the game away.
Take a listen:
That is quite clearly the Overwatch theme given a bit of a Christmas-y feel. This doesn't confirm an event of course, but I think it's pretty close to one. I'd look forward to that.