It should be accepted that Russia will not withdraw from South Ossetia or Abkhazia. This matter little. Georgia did not have substantive control of these regions before the war anyway. Regarding defensive position against Russia, the Georgians can still cut off the Russians by taking out the Roki tunnel, as well as applying the choke at the pass across the Caucasian mountains when needed. These actions can be accomplished in my opinion without requiring air control if they are appropriately armed with missiles and or unmanned drones. Meanwhile, the Georgians and still infiltrate and destabilize both regions (as will the Russian attempt the same against Georgia)
What to do if Russians do not withdraw from Georgia proper? I believe this will be a significant tactical and strategic error on their part. If they wanted Georgia, they should have taken it before international support came to Georgia. Now with the US airlift, the Georgian could be re-armed as well as upgraded for an irregular war against Russians. Unlike Chechnya, who were not supported by the West, Georgia has a direct support line and defensive mountainous terrain, making them more like Afghanistan in their struggle against Russia.
Russia has nothing to gain by staying in Georgia. Whether they are smart enough to acknowledge this remains to be seen.