The two are related, but the double XP is not in celebration of the sales. The double XP weekend – happening from Friday – is to celebrate the release of ‘Annihilation’. While the latest DLC may only be available on Xbox Live, the double XP will be across all platforms.
In the related portion of news, Black Ops became the biggest selling game in the UK, breaking Modern Warfare 2’s record.

It wasn’t going to be a day that would pass by without a Gears of War 2 XP event, now was it? American Independence Day will see a 21x XP boost along with a few Horde tweaks.
To celebrate the release of the new
Starting today at 9am (PST) [4pm GMT] and running until 12am (PST) on Monday 30 May, you will earn double XP in Crysis 2 across all three platforms.
As part of the celebration of the return of the PlayStation Network, Killzone 3 is offering you double xp for this weekend until Monday, May 23 at 10am [UK time].
Two (one can say slightly related bits of news) regarding the PlayStation 3, and for a change it’s two bits of good news – if you like shopping on the PlayStation Network Store and enjoy playing Call of Duty: Black Ops that is.