The Sefas Emes writes that the geulah from Mitzrayim was not just a one-time historical event, but it was the blueprint for all future geulos. “Ehyeh asher eheyeh,” the promise, as Rashi explains, that just as Hashem was with Bnei Yisrael through galus Mitzrayim and brought them to geulah so too in all future tzaros and galiyos will he do the same, means that this geulah from Mitzrayim is the paradigm that will shape and repeat itself in all future redemptions. Moshe Rabeinu’s question was not prompted only by concern lest his fellow Jews in Egypt not believe in the geulah – his particular circumstance -- but rather it was a question of meta-significance, a question about the blueprint that would be used for all those future generations. Can redemption come to a people who are unsure and unsteady in their emunah? Moshe wanted Hashem to affirm that such a thing was possible and would be built into the plan. Whether his generation needed it or not, a future generation might.This yesod helps explain another puzzling aspect of Moshe’s dialogue with Hashem. After asking Hashem what he should tell Bnei Yisrael G-d’s name is and getting an answer and a reassurance that his message would be heard by Bnei Yisrael, Moshe then argued that he can’t speak clearly and therefore should not be the go’el. Why did he ask Hashem to reveal his name and only then say that he is not prepared to go? It’s almost like Moshe wanted to take advantage of the situation and get to G-d reveal his name even though he didn’t want to take the mission anyway.
The Sefas Emes answers that the revelation of Hashem’s name as “Ehyeh asher ehyeh” was not just about what to call G-d, but rather was a revelation that this geulah from Mitzrayim was going to have meta-significance as the blueprint for all future geulos. Once Moshe understood that key point, he used it as new ammunition to argue that he was not the right go’el. Moshe already foresaw that he would not make it into Eretz Yisrael; a geulah through his hands was going to be an incomplete geulah. What Moshe did not foresee is that his neshomah is the shoresh of all the future tzadikim who would help deliver all those future geulos, so what was incomplete in his lifetime would eventually come to fruition.