It will sell very well. I expect it will sell at around 100 Millions in the first day and 150 Millions in the first week. Probably a Billion in a year and become the greatest thing the mankind have ever witnessed. God bless and only bless halo, for Masterchief is love, Masterchief is life! Masterchief is everything.
Now in all seriousness :3.
2 Millions-2.5 Mills in da first week and probably 6-7 millions by the end of next year or next Halo. It's a very realistic number since Microsoft advertising this like TONs !!! i have seen it on TV, on Internet website, on Facebook ads, GameStop, Wallmart, YouTube ads, etc and etc.
Not to mention dat Halo have a much bigger fanbase than some of u might think. Mainly helped by excellent community like Red vs Blue.
Tbh, as a huge Sony fan. I'm jelly.
