Dislocated knee caps (which Orton claims to have) is only an injury that takes 2-6 weeks, at most. If Orton's kayfabe injury isn't surgery required, his injury would only realistically keep him out 2-3 weeks. I'm guessing the injury was mostly used as an excuse for Randy losing to Miz. It works both ways, not only does Randy look AS bad as he would losing to young superstar like Miz if he were completely healthy, but Miz also makes himself look good in the process, putting him over with the WWE championship and beating a future WWE Legend in the process.
I expect Randy to be fighting for the WWE championship in either a one on one match with the Miz (possibly being a TLC match) or a fatal four-way with Miz, Orton, Barret, and one mystery person. They can use the mystery person as a trap, getting viewers to believe this person is John Cena. Cm Punk would be perfect for this, unfortunately his injury prevents this. That mystery person could be Triple H though, I assume he is ready to return by now, and with all the hype from John Cena, everybody has already completely forgotten about The Game. He can show up in the Fatal Four Way, and possibly win the title.
A Triple Threat TLC match would be perfect, Miz, Orton, and Barret. When's the last time we've seen one of those. Not only does it give the current superstars in the title picture, but it also keeps the stipulation of the show, and Barret can get used to such extreme stipulations, and develop his in ring ability stronger. We don't see these 3 superstars fight in Ladder types of matches often, even Orton. A match where both the champion, and his contenders are in experienced in, will be perfect to see who wants and deserves the title the most.
Unfortunately I don't see Orton regaining the title until after Wrestlemania. We will most likely see him in the Royal Rumble, and if another feud hasn't developed, in the Elimination Chamber as well. The way the WWE is pushing over Miz and Barret, and the way the promos are going, Randy Orton just seems unlikely to regain the title, just because his in-ring ability, and character can be used in a more exciting feud at Wrestlemania.