Pup,
The veil which cloaks our remembrances allows recognition of the truths we knew, and also understanding of Eternal Laws... IF we are receptive, these precious truths will be revealed to us from Jesus Christ and the Holy Spirit.
But according to LDS doctrine, individuals can't receive revelation that would affect the entire church, such as "X is an enternal truth but Y is subject to future revelation." That's what you're doing--choosing what's X and what's Y and announcing it to everyone, without scriptural backing.
For example, according to LDS doctrine, a father could say that God revealed to him that his child should be homeschooled, because he has stewardship over his child and that's the kind of thing God might reveal to him. But God wouldn't say, "your wife should receive the priesthood," without also giving the revelation through the prophet, because that affects the policies of the whole church. Other members would have the right to ignore
that message and say that it wasn't from God, while an obedient child should accept that God told her father how she should be educated.
The above is pretty solid LDS doctrine, as far as I understand. For example:
http://www.lds.org/ldsorg/v/index.j...toid=32c41b08f338c010VgnVCM1000004d82620aRCRD
What you're saying affects the whole church. Unless the prophet, speaking as a prophet, has said that the ban on homosexual acts or marriage will never be lifted, I think, according to church doctrine, such a statement from an individual member could be ignored as not necessarily an accurate reflection of God's intentions.
I would have thought the standard, doctrine-based LDS answer to: "Will the church ever approve of gay marriage?" would be: "We don't know, but if God wants us to, he will reveal it through the prophet"--leaving open the possibility.
Oddly enough, my wife, a current member and returned missionary, answered just as you did and disagreed with my proposed answer above, and she's usually pretty solid at doctrinal sources, but she also couldn't offer a doctrine-based reason for how she could know which things were eternal and which might be subject to future revelation.
I wonder if this is a case where the cultural aspect of the church outweighs the doctrine-based aspect, and the idea of gay couples being married in the temple is just too squicky for conservative church members to contemplate.