The order of prayer has the following:
- Ingathering of Exiles
- Rise of Sanhedrin
- Building of Jerusalem (the Beit haMikdash)
- Moshiach ben David
- Return of the Shechina to Tzion
Why would the return of the Shechina to Tzion be last? But rather, the return of the Shechina to Tzion is a cause for the building of the Beit haMikdash (see here). To me, it appears that this is a hidden teaching implying the sin of Adam haRishon.
- If we are worthy, and we do not repeat the sin, then the blessing there is the ancient blessing (which many people heard yesterday during Musaf): Blessed are You, Hashem, that only You we will serve in fear.
- If we are not worthy, and the sin is repeated, G-d forbid, then the blessing here is the one that we use today: Blessed are You, Hashem, Who returns the Shechina to Tzion.
If the sin is repeated, only the Hand of G-d can repair the damage, which is different from the Nesirah, which is a sort of natural process.