Albert Barnes on 1 Corinthians 13:10

But when that which is perfect is come. Does come; or shall come. This proposition is couched in a general form. It means that when anything which is perfect is seen or enjoyed, then that which is imperfect is forgotten, laid aside, or vanishes. Thus, in the full and perfect light of day, the imperfect and feeble light of the stars vanishes. The sense here is, that in heaven--a state of absolute perfection--that which is "in part," or which is imperfect, shall be lost in superior brightness. All imperfection will vanish. And all that we here possess that is obscure shall be lost in the superior and perfect glory of that eternal world. All our present unsatisfactory modes of obtaining knowledge shall be unknown. All shall be clear, bright, and eternal.

(b) "But when" 1Jn 3.2