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.