Friend troubles?

ok so i am a freshman but im really mature for my age and my closest friends are all seniors, and as graduation approaches i get kind of worried about what its going to be like next year. sure i have some friends that are also freshman but im not as close with them, and i sometimes feel weird when hanging out with them because they dont really talk about the same things i do with my senior friends. I really dont know what to do because next year i dont want to be friendless, any ideas that doesnt involve me kicking my seniors to the curb?