The question and answer here
Touch on the idea that the donkey that Moshe rode (his family and placed his belongings on (not him himself, the current translation in that answer is false)) back to Egypt is the same donkey that Avraham saddled for the binding of Yitzhak, and the same donkey that Moshiach will ride on.
Later in the sicha that's quoted in that answer it brings anther Midrash that says that it's the son of the donkey who's (mouth?) was created during the 6 days of creation.
It's not clear if Bilaam's donkey (whom the angel killed) was actually created during twilight on erev shabbos bereishis, or if just the mouth (which could also be some kind of spiritual power that later allowed Bilaam's donkey) to talk.
Since the earlier Midrash implied that it's the same donkey that interacted with both Avraham and Moshe, who were hundreds of years apart, and that Moshiach will interact with it thousands of years later, and that this donkey was the "son" of Bilaam's donkey, that implied that even Bilaam's donkey was alive for thousands of years prior to it's execution
(And maybe that's why the angel specifically had to kill it, because if not maybe it would have lived forever, and that's why "people would say that this is the donkey that outsmarted Bilaam),
Which strongly implies that the actual donkey itself was created erev shabbos at twilight
(Although if so it would be after the creation of all other animals, and even after the creation of man. Usually based on the other aggadic teaching regarding the order of creation, that man can be looked at both as the highest level (the last in action is the first in thought) or lowest (being that even inanimate matter preceded him), and if the donkey itself (not just the mouth) was created after man, then really this specific donkey would be greater than all of mankind (according to one perspective), which would be a big novelty to say.
However if we say that only the mouth, the potential for the donkey to speak, was created then, then maybe there could be an explanation for how that is even greater than man, since it was what attempted to get Bilaam to do teshuva, but I haven't seen anything like that written, so that would still require further clarification.
Also if only the mouth was created then then it's still not clear why it's implied from the other Midrash that even the mother lived thousands of years.)
Anyhow, it stands to reason that the offspring of something would share it's characteristics.
Seemingly, according to at least the straight forward way of understanding the Midrash and the sicha, both the mother donkey and her son lives for thousands of years, which implies it at least inherited that trait.
Are there any sources or commentaries which discuss if the son donkey will also inherit the power of speech?
True that it says that Hashem had to "open" the mouth of the donkey to get it to speak to Bilaam, implying that talking wasn't it's natural occurrence but rather a result of a miracle at that time, but still:
It would stand to reason that the son, already sharing the characteristic of living thousands of years, would also have a similar characteristic, that maybe it's born with a "closed" mouth that would be opened at some future time, and
It stands to reason that something created ah the end of creation, even after the creation of man, would serve an eternal purpose (similar to the tablets writing that was created then which exists forever (tzarich iyun regarding the first tools)), so it would make sense that the mouth of the donkey would have an eternal effect, if it relates to the donkey of Moshiach them maybe that could add to the explanation for why it was created after man (and thus has an aspect that's greater than him), since the time of Moshiach is the ultimate purpose of creation etc etc.
Are there any other commentaries that deal with this?
Regarding what the mouth represents in terms of the Sefiros I got some answers from the Ask the Rabbi department at chabad.org, maybe can be a starting point
Zohar Balak 201b, 210a
Toras Menachem 5733 Volume 4 pp. 71-75
Zachar Chasdo Volume 4- Bamidbar Balak Maamar 18.
There is explains that the mouth of the donkey is the Sefira of Daas. He explains that the three mouths are Chochma, Bina, and Daas.