Well, I've been speculating on this very same thing, much like you. I believe that if the virus has a reason to adapt further, then we could see changes, perhaps drastic ones. I'm not sure if an adaptation to make the zombie smarter would be practical. One of their strengths is their stupidity because if they were smarter, then they may become self aware and question their hunger for flesh. As for Faster and stronger zombies, my theory is that a zombie can not become any stronger or faster or smarter than it was before it was infected. In fact, a zombie could only get weaker over time. The only thing that gives them an advantage over humans is that Zombies never fatigue. They will keep pushing themselves until they quite literally fall apart.
Although too many people round these parts don't seem to be blessed with the intelligence we've been given, you seem to have it on lock down. Zombies will not get smarter, or stronger or faster. These are atributes of a living, breathing, heart beating human. A zombie is none of those things...is this topic really that intriguing? Wait, it can be, but 90 percent of you have no idea what you're talking about. It's science, it's medical, it's common sense. A lot of people should do some damn research before opening their mouth. But you Tyler, I can carry a conversation with you...Thanks for the great post....
It seems that the only thing that makes zombies scary is that the virus disengages the self preservation part of our brains. And as far as the getting smarter...It could happen. Most people tend to dumb themselves down for whatever reason. So if we shut down personality and desire, then would the intelligence we ignore suddenly kick in? And what about the survival instincts that we need but have been taught to ignore? What if those kick in? then we my friends are screwed.
You're taking the thought of mutating waaay to far. In all likelihood, if it was to mutate, it would be to a form that would be easier to transmit. Probably airborne. Or, if it already was an airborn virus, but the survivors would have had some sort of immunity to it, which is why they survived the virus itself, it's mutation would probably be to a form that could get past the immunities.
And that, my friends, is far scarier than fast zombies, smart zombies, or any other type of zombies, because there would be no defense.