Don't think this will affect CoD sales. Halo 4 showed two mega blockbusters can launch nearly simontaniously and still sell great. That is why they are mega franchises, a lot of people think they are must have games. If CoD sales are lower it will be decline from franchise fatigue, not GTA.
This could have a huge affect on nextgen consoles though as mentioned. If all the big games are still coming out on the 360 and ps3, why would anyone but the most hardcore gamers update. Grand Theft Auto, Call of Duty, etc. will satisfy the majority of gamers this holiday. There won't be any enthusiasm for new consoles.
To make matters worse it seems like nearly every third party developer that is making a next gen game, is going to make their games crossplatform between nextgen consoles and current gen ones. Will gamers think the graphical update is worth the investment of a potentially $400+ console. I don't think so.
Hopefully I'm wrong but I think early console adoption will be as abysmal if not worse than the wii u. At least Wii U has the advantage that most of its big games are first party. Microsoft and Sony have a big problem because a lot of their console's biggest franchises are third party, and third parties will be more focused on software sales than making nextgen consoles must haves.
