It is possible that Eliyahu Hanovi has already come

Sicha of the Lubavitcher Rebbe, 18 Tammuz 5751

Tammuz is referred to as "the month of redemption." [...] The connection to the redemption is further emphasized by this week's Torah portion, Parshas Pinchas. Our Sages identify Pinchas with Eliyahu, the prophet who will announce the redemption. It is possible that Eliyahu has already come and has seen the coming of the Mashiach, but that his announcement has not reached us as of yet. The ultimate redemption is unique, for when it comes, it will come in a complete and total manner. In this, we see a contrast to the other redemptions from exile. The previous redemptions came in stages, while the future redemption will be immediate and total.

Revelations of the future

Discourse of the Lubavitcher Rebbe, Pinchas 5748

The revelations [which come about through the service of the soul after it descends below to this world] will be in the time to come when "the glory of Hashem will be revealed and all flesh together will see that [the world exists] because the mouth of Hashem speaks" (Yeshayahu 40:5). From the fact that it says all flesh it is understood that the intent is not only Yisroel, but that it includes all the nations of the world (see Tanya ch. 36). And more than this, that "all flesh" includes also animal, vegetable, and mineral, that in all of them will be revealed the "[the world exists] because the mouth of Hashem speaks."