Haha. He hardly picked up a racket when he was over there. Partly because of a lack of decent hitting partners, partly because he was busy doing other things.
Not many college athletes spend a semester abroad because, yes, you do miss out on a lot and your game will suffer. There is no such thing an off-season. Tennis is a high maintenance game so coming back from time away is a process in itself, and on top of that the other guys have been training year round.
That said, if you do decide go abroad, just enjoy your time there while you can and don't dilute your experience by focusing so much on tennis. Take in the sights, learn about the history and the culture, speak the language, try new foods, drink a lot of wine, take weekend trips with other student travelers.