No. More often than not, I see people change for the better. In fact, I can't even think of one person I know who has changed in a negative way (though I'm sure they're out there). Change, for the most part, is a wonderful thing, and it means that people are growing rather than stagnating or, in several cases I've seen, wallowing in a hole they dug for themselves. When people like that don't change, I have to let them go if they become too burdensome (I try not to, though, until there's no more I can do).
Old friends I've reunited with after years have changed, but though I'm not as close to them anymore, they're still the same people, and we're still good friends. When you pass from the end of middle school, through high school, and on into young adulthood, what 'changing' really means is discovering who you are after spending all that time trying to find it and experimenting. You may find yourself or others to be radically different over time, but the stuff that you're really made of is still there. If that 'stuff' isn't what held a friendship back in the day, it may well fall through, but it's not the end of the world. There's billions of people out there, so there's always people you can find a real friendship in :3