Only 2-3 times did I have good friends on the major rotations during 3rd year. Even then, I was often on different teams and could only see them at didactics or conference. Sometimes you'll make good friends with people you didn't really hang out with your first two years.
If you sign up for the same electives during 4th year, you could have fun with some old friends...
It probably depends alot on your school, how many students and different sites you have, too...but years 3 & 4 just aren't as social as the first two.