It's a ritual phrase to conclude the Passover, meaning "God willing, we'll all be doing this in Jerusalem next year." Because no matter how rooted the Jewish family is in the diaspora, there's always a little nostalgia for the homeland.

I've seen it commonly used as a toast when wishing for something in the somewhat remote future, especially since it can be interpreted as a wish for the messianic golden age to arrive (at which point everyone would presumably be gathered in to Jerusalem).

Luckily, I think you have considerably better chances of catching up on One Piece than any of us have of witnessing the coming of the biblical messiah. ^_~