Although it sounds incredible, after a few months, you will barely even THINK about your high school friends. College is an amazingly transformational experience, and no matter how much you try to stay in touch, I think you will find yourself changing rapidly into an entirely different person...as will your friends. Friendships are only stable over time when both sides either a) don't change much (which is true of later-in-life friendships) or b) change in the same direction. The chances of b) happening are slim to none. Even if you go to the same school, you will meet and live with different people, have different experiences, and change in different ways.
It's OK, though -- you'll make more friends, and be too busy with work and fun to think about your old friends too much. The people who are REALLY special to you will stay in touch, and you'll find yourself making time to spend with them as well. The people whom you never seem to call...well, that is the filter of your true priorities being applied to your life. Enjoy your time now, exchange numbers, and say your goodbyes...but be ready and willing to experience new things and people this fall.
College friendships have a better prognosis, but it's REALLY hard to be super-close to people who are more than a year or so behind you. Once I was out in the working world (even before, to some extent), it was just flat-out funny to hear people talk about their lives being so complicated and stressful because of exams or which party to go to next week. At the time, it's the hardest thing you can imagine -- "oh my GOSH I have two finals in ONE day!" -- but it's funny how having real responsibilities (family, career, etc.) puts the college experience into perspective. I couldn't stay in touch with ANYONE from high school when I went to college -- way too f?cking kiddie. The first time you go back to a HS football game after you graduate, you'll understand.