More or less an inevitable change, really.

Any reasonable student of history can point out that homosexuality has never been a quality that decreased one's ability to wage war. If anything, history might suggest that it was a "plus" for soldiering.

During the transition, unit cohesion will, initially, suffer and openly gay serving will bear the brunt of ostracism and some abuse. Neither the loss of unit cohesion nor the ostracism will be as crippling as their respective proponents are asserting at the present time. As higher-ups police this up a bit, the culture will begin to change. We did this in the 1950s with race -- took a while, but everyone learned the lesson and we were better for it in the long run. While sexuality and race aren't directly parallel, I think you can make a good parallel of how things will change.

Women serving in combat should work the same way. Some roles/specialties will be largely unavailable to women based on purely physical requirements -- but those same requirements should be screening out a lot of the swinging richards as well. Set the appropriate standards and whoever meets those standards can get the billet. However, Israel supposedly had some evidence that women casualties were disproportionately distracting to male soldiers -- might be something that has to be looked into.