I concur with those who answered "no". People have been asking for a futuristic Call of Duty for years now, and Treyarch is providing. I admit that when I first heard about Treyarch's plans to make Black Ops II take place in a futuristic setting, I was skeptical and worried about exactly this; I didn't want Call of Duty to become an entirely different kind of game, or morph into some un-realistic futuristic shooter. But it isn't.
When people hear the word "futuristic", they immediately begin to conjure up images of Star Wars and other science fiction films and video games. I'm guilty of this as well. But Black Ops II takes place in 2025, far from the era of starships and intergalactic warfare. I think we can all rest a bit easier knowing that this game is set only a bit over a decade into the future.
Another major concern to be had when developers venture into the realm of the future is feasibility. In other words, can they create an environment that is innovative and advanced, but simultaneously something that could actually happen in the near future? As interesting as Call of Duty space battles would be, it would completely destroy the aspect of realism that Call of Duty has strived for (although in a less serious manner than its competitors). Treyarch, as we saw at E3, has been doing their homework. They've researched military equipment thoroughly, and have drawn from that. With Black Ops II they're making an educated guess as to where we'll be in a bit over a decade from now.
In short, no, I'm not worried. We've seen enough of the game to know that this isn't going to be reminiscent of Star Wars, and that the core of Call of Duty gameplay is still very much intact. If you've enjoyed previous Call of Duty titles, I think you're bound to enjoy this one too.