The understood words "we will see" can be supplied. Seeing face to face is a metaphor or synecdoche for being physically present with the one we will see. Alternate translation: "but then we will see face to face" (See: [[rc://en/ta/man/translate/figs-ellipsis]] and [[rc://en/ta/man/translate/figs-metaphor]] and [[rc://en/ta/man/translate/figs-synecdoche]])