I say this is possibly one step closer to gays being allowed to serve openly. Most likely the full removal of DADT and the code that actually keeps gays from serving in the military will go away within the next year or two, but could possibly take up to 5 (don't really think it will take 5 years, but you never know). I don't really know how long this injunction will last or if the military will even abide by it.
I do see a couple of possibilities. 1) The military completely ignores the injunction and puts out people anyway under DADT. Most likely this case will go further, so once a final decision is reached, then the disposition of those put out after the injunction was ordered would need to be included in the ruling. Otherwise, there is just going to be future court cases concerning those members. 2) The military respects the injunction until the DOJ can get an appeal filed and another judge/court to remove the injunction. Now, it might happen that they can't get the injunction removed during the entire process, but it seems that these cases go back and forth, so it is possible. Any discharges under DADT now and in the near future would be put off until a different verdict is given, if they ever get one.
Overall though, DADT should be gone shortly. (And, by DADT, I am personally referring to the code that keeps military members from serving in the military as a whole, not just the "Don't Ask, Don't Tell" part.)