Jamieson, Fausset and Brown on 1 Corinthians 4:8

8. Irony. Translate, "Already ye are filled full (with spiritual food), already ye are rich, ye have seated yourselves upon your throne as kings, without us." The emphasis is on "already" and "without us"; ye act as if ye needed no more to "hunger and thirst after righteousness," and as if already ye had reached the "kingdom" for which Christians have to strive and suffer. Ye are so puffed up with your favorite teachers, and your own fancied spiritual attainments in knowledge through them, that ye feel like those "filled full" at a feast, or as a "rich" man priding himself in his riches: so ye feel ye can now do "without us," your first spiritual fathers (1Co 4:15). They forgot that before the "kingdom" and the "fulness of joy," at the marriage feast of the Lamb, must come the cross, and suffering, to every true believer (2Ti 2:5, 11, 12). They were like the self-complacent Laodiceans (Re 3:17; compare Ho 12:8). Temporal fulness and riches doubtless tended in some cases at Corinth, to generate this spiritual self-sufficiency; the contrast to the apostle's literal "hunger and thirst" (1Co 4:11) proves this.

I would ... ye did reign--Translate, "I would indeed," &c. I would truly it were so, and that your kingdom had really begun.

that we also might reign with you--(2Co 12:14). "I seek not yours, but you." Your spiritual prosperity would redound to that of us, your fathers in Christ (1Co 9:23). When you reach the kingdom, you shall be our "crown of rejoicing, in the presence of our Lord Jesus" (1Th 2:19).