It's sold 6,443,550 copies after 6 weeks on sale.
It outperformed my prediction for this week by a whopping 128k!
It's outsold my predicted sales every week except week 1.
It took Halo 3 13 weeks to sell as much as Halo 4 has in 6. It took Halo: Reach 14 weeks to sell what Halo 4 has in 6.
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