The Sefas Emes explains that we hide part of the afikoman, tzafun=hidden, because not all of the geulah was revealed during yetzi’as Mitzrayim. All of the subsequent galuyos and tzaros we have suffered for millennia are but a taint of galus Mitzrayim that never worked itself out; the geulah which we are ultimately waiting for is really the completion of the process that only began with the redemption from Egypt.
In “Dayaeinu” we go through a laundry list of “ma’alos tovos” that Hashem has done for us, starting with taking us out of Mitzrayim and continuing through binyan beis hamikdash. Why is this whole list recited at the leil ha’seder – what do all these things have to do with sipur yetziyas Mitzrayim? The Sefas Emes again sees this as evidence that Jewish history is the unfolding of geulas Mitzrayim in all its glory.
(Perhaps the machlokes Tanaim whether the ultimate geulah will eclipse the need to have a zecher l’yetzi’as Mitzrayim is not about whether yetzi’as Mitzrayim will ever be forgotten [which would beg the question of why it is counted as a mitzvah], but rather about which format the mitzvah of zechiras yetzi’as Mitzrayim will take. Perhaps remembering [after we are zocheh to see it] the ultimate geulah is itself a kiyum of zechiras yetzi'as Mitzrayim as it is the ultimate culmination of the yetzi’as Mitzrayim process.)
So yes, it’s isru chag, Pesach is over, and I hope you already had your bread or a cookie. But we are by no means done with yetzi’as Mitzrayim, as we still await the completion of our personal and national redemption.