IMHO, if you suddenly got dropped into 50 years from now, you would still see something that was very familar. There will be a few more options, refinments in materials, perhaps even non-metalic casings. But other than that, I don't expect to see much change. Remeber, the bullet itself functions because it is a dense mass. If a synthetic could be made that had greatter density than what we can get with current metals, then it will be adopted.
Powder will continue improving. I expect that certain things like tagints and tracers will become common, but overall, it will be something that you would recognize and rapidly become comfortable with.
I believe we'll see electronic firing systems fairly soon, certainly within the next ten years or so. They will just be so much cheaper to make and require nearly NO hand work. I'm not looking forward to that but I do believe it's inevitable.
But the big thing is that the vast majority of guns avialable, in the general population, 50 years from now will be the very same guns that are in circulation today. When I look at the firearms I personally own, almost all are over 20 years old, about half are over 50 years old and several are nearly 100 years old. They all still work and I shoot them regularly. I see no reason that trend wouldn't continue.