All these are valid fears. It just shows that you are looking ahead, trying to see how the horizon looks like. But out of all the fears that you listed here, I'm sure your friends will stick with you wherever you go. Those select few people thqt you care about will still find a way back to you no matter how far apart you may be. Sure, you'll feel each other drifting away but that's just because you're all going to be busy. But once the dust settles and you all have found your groove, you'll still find yourselves hanging out, chatting, and having fun as if nothing's changed.
Just have fun, and continue to learn.
This made my heart feel at ease. I just hope that even if we're million miles apart, the connection, the bond, and our love for each other will still remain.