Were the Revenge-class ships planned with five turrets?

Was the Revenge class originally intended to carry five twin 15-inch turrets?

No. A fifth turret would have required a materially different hull and superstructure arrangement.

The historical Revenge layout cannot accept another mounting as an unused option. Adding a fifth twin turret would require lengthening or reorganizing the central part of the ship and changing the space between the funnel and after mast. Those changes would affect magazines, machinery, structure, and the ship's overall proportions. A turret plan is inseparable from the hull designed to support it.