[L]et’s say for instance that the [DADT] injunction is upheld and it takes a couple of years for the core case to get to the Supreme Court, where everyone expects this to be decided. If the Pentagon has lifted DADT for two years and the military has not suffered any notable ill effects from its gay and lesbian members serving openly, how likely will it be that the Pentagon will reinstate the old policy? Congress will be under pressure to maintain the new status quo if no problems arise from it, and if Obama is still in office, he will press Congress for action to rescind DADT. In fact, he will have more latitude in doing that with Republicans in charge, since Obama won’t have to worry about embarrassing the Democratic leadership of the past two years on the subject any longer.
I don't think the injunction will be upheld. But this is an interesting and plausible scenario if it is.