Ok, having lived on both sides of it, I will tell you what will happen. By making Friends, and being more sociable, I assume you mean partying and really experiencing college, as everyone should. Well...it depends.
I was out of control in high school. I was partying every single day (tipsy tuesdays, wasted wednesdays, thursday throwdowns, fuc*** up fridays, ****faced Saturdays, and Stoner Sundays<= to kill the morning after hangover) was pretty much my moto, as well as my group of friends. People who read this may think I am trolling, but I am dead serious and I would also argue that I partied much harder than most college students. I was sociable w/ everyone, but I was an academic ***** (2.9 high school GPA). Once I entered college, I was REALLY serious about my grades, and I shocked everyone. I got the grades, an I aimed for perfection like you ( i had 3 semesters in a row where I made presidents list, taking 14, 17, 18 hrs).
I would honestly say that, it depends on your friends. I think it is completely justified to sorta of shut out your friends if they are detrimental to your cause. I did that, and by doing so I achieved that academic goals in mind. But after doing this, I became less and less sociable because like you, I assumed, Well if i become really good friends with this person I am going to have to make obligations and that will take up my "study time".
But Honestly, WE ARE NOT ROBOTS. Everyone needs social interaction to maintain their sanity. I have been on both ends of the spectrum, and I have now found my happy medium. I thought that I could go through college without seeing anyone/meeting new people/ being sociable like i used to because it would harm my grades, but the fact is that we are all going to need that good friend when times do get tough. When you do bomb a class. When you do get mid 20's on your MCAT. I don't care who you are, or how smart you are, MEDICAL SCHOOLS DONT WANT 4.0 Zombies. Doctors need to be able to communicate with people, and you have to love and enjoy the company of others.
So make friends, enjoy college, and be sociable while still working hard to maintain your grades. I promise you that if you don't, your grades will suffer more from the lack of social interaction. Just make sure, as someone eluded earlier, that your friends aren't detrimental to your cause, share your same interests, and will like you for who you are. Being sociable doesn't mean you have to set the new Guinness book of world records for a keg stand. And honestly, if it takes "too much of your time now"...how do you expect to "make friends later" in MEDICAL SCHOOL???