That Paul may have been speaking hypothetically about "tongues of men and of angels" is possible -- what is NOT possible is that Acts 2 is the only instance of Tongues in the New Testament:
Mar 16:17
And these signs shall follow them that believe; In my name shall they cast out devils; they shall speak with new tongues;
Act 2:3
And there appeared unto them cloven tongues like as of fire, and it sat upon each of them.
Act 2:4
And they were all filled with the Holy Ghost, and began to speak with other tongues, as the Spirit gave them utterance.
Act 2:11
Cretes and Arabians, we do hear them speak in our tongues the wonderful works of God.
Act 10:44
While Peter yet spake these words, the Holy Ghost fell on all them which heard the word.
Act 10:45
And they of the circumcision which believed were astonished, as many as came with Peter, because that on the Gentiles also was poured out the gift of the Holy Ghost.
Act 10:46
For they heard them speak with tongues, and magnify God. Then answered Peter,
Act 10:47
Can any man forbid water, that these should not be baptized, which have received the Holy Ghost as well as we?
Act 19:6
And when Paul had laid his hands upon them, the Holy Ghost came on them; and they spake with tongues, and prophesied.
1Co 12:10
To another the working of miracles; to another prophecy; to another discerning of spirits; to another divers kinds of tongues; to another the interpretation of tongues:
1Co 12:28
And God hath set some in the church, first apostles, secondarily prophets, thirdly teachers, after that miracles, then gifts of healings, helps, governments, diversities of tongues.
1Co 12:30
Have all the gifts of healing? do all speak with tongues? do all interpret?
1Co 13:1
Though I speak with the tongues of men and of angels, and have not charity, I am become as sounding brass, or a tinkling cymbal.
1Co 13:8
Charity never faileth: but whether there be prophecies, they shall fail; whether there be tongues, they shall cease; whether there be knowledge, it shall vanish away.
1Co 14:5
I would that ye all spake with tongues, but rather that ye prophesied: for greater is he that prophesieth than he that speaketh with tongues, except he interpret, that the church may receive edifying.
1Co 14:6
Now, brethren, if I come unto you speaking with tongues, what shall I profit you, except I shall speak to you either by revelation, or by knowledge, or by prophesying, or by doctrine?
1Co 14:18
I thank my God, I speak with tongues more than ye all:
1Co 14:22
Wherefore tongues are for a sign, not to them that believe, but to them that believe not: but prophesying serveth not for them that believe not, but for them which believe.
1Co 14:23
If therefore the whole church be come together into one place, and all speak with tongues, and there come in those that are unlearned, or unbelievers, will they not say that ye are mad?
1Co 14:39
Wherefore, brethren, covet to prophesy, and forbid not to speak with tongues.