I am trying to integrate all the facts and thoughts listed below to answer the following question:
Should I hope for the resumption of animal sacrifices?
1-Prayers for rebuilding the Temple and resuming sacrifices are in our liturgy. For example, Amidah blessing 17 [Avodah] says:
Restore the service to the Holy of Holies of your Temple. Accept the fire offerings and the prayer of Israel with love.
Ishei Yisrael -- the fires of Israel -- refers to sacrifices, but the Talmud also uses that expression to refer to 'the righteous of Israel' [Menachot 110a]. Rabbi Soloveitchik believed it refers to our martyrs, the human “self-sacrifices” we have been forced to make in history, l’kiddush HaShem.
2-Many prophets told us again and again: It's not your sacrifices God wants. But they did not try to abolish them.
3-The Rambam taught that sacrifices were not meant to last indefinitely:
The custom in those days among all men…consisted in sacrificing animals. God did not command us to give up these services; for this would have been contrary to the nature of man, who generally cleaves to that to which he is used. Sacrifices [however] are not the primary object [of the commandments about sacrifice], prayers are. [To wit,] we were not commanded to sacrifice in every place, and in every time, or to build a Temple in every place, or to allow anybody to become a priest and sacrifice. Only one Temple has been appointed, and only] "in the place which the Lord shall choose" (Deut. 12:26). In no other place are we allowed to sacrifice: "Be careful not to give your burnt-offerings in every place that you see" (Deut. 12:13); and only the members of a particular family were allowed to officiate as priests. All these restrictions served to limit this kind of worship. But prayer and supplication can be offered everywhere and by every person. Because of this, the Prophets rebuke people for being over-zealous in bringing sacrifices. [Moreh Nevuchim (Guide for the Perplexed), 3:32]
4-But in his halachic writings, the Rambam upholds the traditional vision of the future:
The Messiah... will build the Holy Temple and gather the dispersed of Israel... All the laws of the Torah will be reinstated as before; the sacrifices will be offered, the Sabbatical year and the Jubilee instituted as outlined in the Torah. [Mishneh Torah, Laws of Kings 11-12]
5-The Ramban disagreed and taught that sacrifices had intrinsic value.
6- Israeli rabbis and the secular government are united in banning Jewish visits to Temple Mount. At the gate, you see the sign:
Entrance to the area of the Temple Mount is forbidden to everyone by Jewish Law owing to the sacredness of the place. Signed: The Chief Rabbinate of Israel.
Why? Because rabbis have declared all Jews to be in a state of ritual impurity (tamei), so they must not come close to the Holy of Holies, which is in that area but we don't know exactly where. The rabbis also declared: No exploration, excavation, or prayer on Temple Mount. Jews are even forbidden to fly over it. The ban will stay in effect until Messiah comes.
Only a para adumah (red heifer) can remove our state of impurity. We haven't had one for 2,000 years, and all candidates have been rejected by the rabbis (the last I know of was in 2002). The Rambam says that the tenth and last will be prepared by the Messiah [Yad, Parah Adumah 3:4] Some cynics have argued that the rarity of red heifers and the presence of the Islamic Mosque on Temple Mount gives Jews an excuse not to rebuild the Temple.
7-The Midrash says: In the messianic age, all sacrifices will be discontinued, except for the thanksgiving offering. [Vayikra Rabbah 9:7]
8-Studying the Torah without sacrificing animals may be enough. In the Talmud, God says:
Whenever people read the order of the sacrifices in the Torah, I will deem it as if they had offered them before me, and I will grant them pardon for all their iniquities. [Taanit 27b]
In the Midrash, God tells Ezekiel:
Learning in the Torah about the description of My House is as great as building it. Go and tell the Jewish people to occupy themselves in learning about the Temple, and in that merit I will consider it as if they are actually involved in building it. [Midrash Tanchuma, Tzav 14; Yalkut Shemoni on Ezekiel 43:10-11 (382).]
9-Two thoughts from me: (1) Even though I am not a vegetarian, it makes sense that, if you are going to eat meat, you should see with your own eyes exactly where the meat comes from. (2) Rebuilding the Temple and offering animal sacrifices are separate issues: The rebuilt Temple could be a splendid super-yeshiva and super-synagogue, but not a site for animal sacrifices.
Question: To help me reach a conclusion, do you know of any relevant facts, sources or expert opinions not covered above?