Sister Sage's plan could be revealed in front of Homlander, but the man may be too caught up in his own glory to see it.
Sister Sage returned to help Homelander. The boys season 4 episode 8
Homelander may be one of the most menacing villains ever to grace the screen. But despite his level of villainy, he's not necessarily the sharpest tool in the box, and makes Sister Sage think of him (as much as he's threatened by it.)
While Homelander proceeded to dismiss Sister Sage, the smartest person in The Boys universe, he was able to make unforeseen events happen to the scenario, culminating in Homelander's victory in the season finale. Sage told Homelander that she will be back for "Phase 2", before leaving the building. But a lot of fans on Reddit are convinced that Homelander will be betrayed by Sister Sage somehow.
Some Redditors are convinced that Homelander's days of supremacy are numbered, given that Sister Sage wants to make the character "like Ceaser." While Homelander is taken by the images of a dictatorial leader popular with the people, Sage can already be plotting his downfall.