You have to first ask yourself and answer the question as to what is "that which is perfect"?
The aforementioned question and answer to it is found in Ephesians 4:13 wherein it discusses 'till we all come to the unity of the faith unto a perfect man, the perfect man being the perfection of the body of Christ: this being then the previous need for the miraculous manifestation of the various gifts noted in 1 Corinthians 12:8-10. We now have the bible to guide us and no longer need the piece meal parts of the body.
Hmm... the NIV and NASB have "mature" here, not "perfect". In English, they are very different concepts.
The "face to face" and "known as we are known" is relating to the distinction between the old testament readings, and coming to Christ via the New Testament and the comparison to the veil in reading Moses, and we now, they then, being able to look into a glass or mirror and seeing a reflection of Christ as opposed to our own image. Ref below 1 Cor 13:12 and below 2 Cor 3 primarily verse 18 to understand what "face to face" is, namely, now we can, as they could, see a reflection of Christ metaphorically when looking into a mirror or "glass" because we now have Christ as they also did then, and are part of him, as opposed to under the old covenant as noted with the Moses comparison or analogy, or when Moses is read as was stated in the scripture.
Stretched beyond the breaking point. It is unreasonable to believe that Paul's
second letter to the Corinthians contains the explanation for a concept presented in his
first letter. You have made the error of anachronism. Further, you're making the argument that Gentile Christians (who are probably unfamiliar with the Old Testament scriptures) would know
and understand an oblique reference to an obscure passage in the Torah.
For your argument to be sound, it must be cohesive, congruent, and complete. You've failed to address the incomplete knowledge and to identify either the "imperfect" or the "perfect" adequately.
Verse 8 notes the pending cessation of knowledge, prophecies (plural), and tongues, all of which are gifts presented in the latter verses of chapter 12. These are all revelatory gifts, and it makes "perfect" sense that when there is no more need for revelation, then revelatory gifts will cease. Are we there yet? No.
If we had full knowledge (as we are fully known), then we wouldn't need to study Scripture. We wouldn't need preachers, and we wouldn't need to debate the meaning and application of Scripture. We still know in part, and still need the revelation that (at times) comes through study and prayer.
We don't yet see face to face. We aren't yet fully mature. We will get there, but not in this season. God still gives revelatory gifts including tongues because His church still needs them.