Guess I'm a bit too late to say "inb4 irrational snobbery and hatred for a decent-at-the-very-worst game".
But anyway, I'd like to see them move the setting forward into the not-not-so-distant future. In other words, laser guns, rail drivers, 'mechs, all that cool stuff, but done feasibly rather than fantastically, in order to maintain suspension of disbelief. Two quick reasons why this is a good idea:
1) Because when you're working with hypothetical weapons that aren't forced to be based at least partially on a real-world counterpart, creating them to have specific roles and be totally balanced is MUCH easier.
2) Call of Duty is a good franchise, regardless of whether or not you're a hipster that thinks refusing to play mainstream games makes you an inherently refined and tasteful gamer, entitled to look down your nose at people that enjoy games for being fun, rather than artistic.