Are you thinking of a fall or winter sport?
Let me advise you to sign up for one.
First off, trying anything is exciting, and the possibility always exists that you may be really good at it.
But there's more. Playing the same sport over and over creates injury risks from overusing the same muscles. I don't mean the player who has a tennis practice once a week all winter, but overdoing it is risky. Different sports require different skills and different muscles.
Playing another sport helps conditioning and stamina. The running in soccer and cross-country may mean that you withstand those third set tiebreaks a little better.
You may become a better team player. Tennis isolates you, and you only know if you helped the team well after your match.. Other sports require different teamwork and make you more well-rounded.
You may even respond to adversity better. If you're a really good tennis player but a mediocre swimmer, the different perspective may do you good.
You meet different people and adjust to different coaches. Good practice for life...which is already in progress.
I know some of you have jobs and plan to give them up for tennis. Jobs are good: they teach responsibility and life skills. But if you don't really need to work, think about a sport instead. You have your whole life to work, and the small amount of money you will earn in a part-time position may someday seem foolish if you regret the things you missed.
Just a thought.