the first thanksgiving

My son posted the following question:

Rav Chaim explains that the Rambam not count the mitzvah of mentioning yitziat mitzraim on a daily basis in his count of the mitzvot because the Rambam says (Sefer HaMitzvot shoresh 3) that only mitzvot that apply forever are counted as mitzvot. When it comes to remembering yitziat Mitzraim, the Rambam rules like Ben Zoma that כל ימי חייך comes to include the night, not the times of Moshiach, when the miracles that will happen then will overshadow everything that came previously.  If that is the case, why is the mitzvah of sippur yitzias mitzraim counted as a mitzvah?  Why will it be still apply in the times of Moshiach and not be overshadowed by the great miracles that will occur then?  

My reply was that the Rambam includes in the mitzvah of sipur (Sh"M 157) not just telling the story of what happened, but "l'hodos al kol ha'tov she'gimalanu," to thank Hashem.  Pesach is the original Thanksgiving!  

You see this in the connection made by Rishonim (Rosh) between matzos of leil ha'seder and the 3 types of matzah offered with the korban todah.

You see this in the shitas Rama that hallel on seder night must be completed before chatzos.  R' Soloveitchik explained that hallel of leil ha'seder is part of the mitzvah of sipur and therefore must conform to the time boundary of the mitzvah of sipur, which is chatzos.  

The Maharal makes the same point, quoting the gemara (Meg 18) that darshens  דא"ר אלעזר מאי דכתיב (תהלים קו, ב) מי ימלל גבורות ה' ישמיע כל תהלתו למי נאה למלל גבורות ה' למי שיכול להשמיע כל תהלתו אמר רבה בר בר חנה א"ר יוחנן המספר בשבחו של הקב"ה יותר מדאי נעקר מן העולם שנאמר (איוב לז, כ) היסופר לו כי אדבר אם אמר איש כי יבלע.  A person is not allowed to add extra praises of Hashem to his brachos because a person can never exhaust all the praise Hashem should receive.  Therefore, we just say what Anshei Knesset HaGedolah instituted and allowed for us to say, no more and no less.  How then can we say on Pesach night that  "kol hamarbeh harei zeh meshubach?"  

Maharal answers that there is a difference between offering praise and offering thanks.  If we take the initiative and try to offer praise to Hashem on the level that He deserves, we will never be able to say enough.  But if Hashem has given us something and we are coming to express our thanks, to stop short of attempting to say all we can would be a mark of ingratitude and selfishness, kafuy tovah.  The mitzvah of siupr is not one of praise, but one of thanks.

Therefore, while in the days of Moshiach there may be other miracles that we have uppermost in our minds and that we express our praise of Hashem for, when it comes to giving thanks, when it comes to sipur, we can never forget and never exhaust the words of gratitude that we owe.