Call of duty is still the juggernaut when it comes to fps sales.
It however did slip with the generation-transition (also cod ghosts is crap)
Destiny is the big new IP with 500! Yes 500 MILLION dollars budget, a large amount of that will be marketing.
New call of duty could POSSIBLY suffer from franchise fatigue. With Destiny, new IP, it has ~2 months advantage, and Activision seemed to put more behind Destiny this E3 than Cod.
Infact, beyond the gameplay vid of Microsofts presser, AW wasn't mentioned too much out of typical previews. While it looked nice, I don't think it really majorly wow'ed anyone (especially here on vgc and neogaf)
Despite that, lots of people will buy cod for the sake of it being cod. Activision are clearly pushing destiny to be the next big cod-like sales game.
I think with sony's strong push, and a lack of a real PS4 must have exclusive this holiday, and that september is relatively quiet for games and new releases, destiny could probably dent cod, I dont think it will outsell in 2014, but it may pick up steam into 2015.