I wouldn't schedule vacation around this date just yet. I feel bad for all the people that locked in on "end of Q4" and now have a week to...well...enjoy the holidays. Maybe it's not so bad after all.
If anyone is considering taking time off, I would advise the week of Jan. 22-26 instead. Planning time off around an MMO patch day, let alone full-scale release day is, as a rule, a horrible idea. Anyone who started out on the US servers Mal'Ganis, Archimonde, Khadgar, or Dalaran for WoW's release can attest to that.