Hmm...looks like VGChartz prediction of 550k for Halo 4 in the US in its 2nd week was a bit off.
US actuals: 477,530
Soo...worldwide this week should actually be ~670k
In % terms this is quite a healthy drop. :)
My prediction threads:
Wii U will sell under 40m units (made on 14th September 2012)
PS Vita will sell under 20m units (made on 30th September 2012)
Wii U will sell under 7m in 2013 - I was right