The old guard will die.
Every new generation following it, is more open minded than the last. They possess their own cultural upbringings. Over 70% of 18-25 year olds voted pro-gay marriage in California. If they join the army at 18, it doesn't erase the values they grew up with. The environment will not change the mind set of people that have been accepting most of their life. Eventually, those people will comprise at least half or more of the armed services. Over time, soldiers became more accepting in Israel. The same will happen in America. The majority evolves. That is just human nature.
Nonetheless, there will always be homophobes. And prejudice for everything under the sun. People will dislike each other for a multitude of reasons. Gay is just another one.