“On that night we were redeemed, and on that night we shall be redeemed.”
The Passover Seder is made up of two halves, roughly divided by the festive meal itself. The first part commemorates the redemption from Egypt as we retell the whole story of the departure from Egypt, starting with “Avadim hayinu, we were slaves to Pharaoh in Egypt, and Hashem our God took us out from there with a strong hand and an outstretched arm.” The second half concludes with the famous line, “Next year in Jerusalem!” our declaration of hope for the final redemption, when Jerusalem will be restored as the holy city and the source of Torah for all the nations.
According to Rabbi Yitzchak Sender in The Commentators’ Haggadah, the second half of the Seder begins after the meal and the third cup of wine, when we pour another cup for Elijah the Prophet, and open the door to see if he’s arrived yet. (There’s lots of additional explanations for opening the door at this point, of course.)