The fudge!Halo 5 did worse than Gears 3.
It will decline from the old games and Halo 5 should be able to reach 6m+ so I'd say no chance
Halo 5, according to what we have for NPD
(October 27th release day)
October = 935k
Next Month = ~358k
Total = ~1.3 million
Gears of War 3
(September 20th release day)
September = 2.0 million.
In just 10 days, GeoW3 sold more than Halo 5 did in 30.