He would have still been a top name because he had already been one for the previous four years but I don't think his continued presence on the show would have gotten in the way of newer stars like Punk, Bryan and Sheamus getting their push. The fact is, by the time he retired, Edge had already won a bazillion world titles and had so many big moments and feuds that I feel they would have of been intent on pushing other stars regardless. I personally think he'd kind of fall into the role Shawn Michaels fell into during his second run from 2002 to 2010, where he involves himself in big feuds and big matches (including challenging for the world title on occasion) for the remainder of his career to stay relevant, but hardly ever wins the world title (Michaels only had a one month reign with the WHC during his second run, and I think Edge would have more than THAT, but not much more. Edge's main time in the main event was already spent.)
As for 2011 specifically, this is how I see that going: ADR still wouldn't have won the World Heavyweight Championship at Wrestlemania 27, because that match happened before Edge received the news of his forced retirement. But he may have won it at Extreme Rules and if that happens, he likely keeps the title well into the Summer and never wins MITB and never cashes in on Punk at Summerslam. ADR maybe feuds and retains the title against Christian before dropping it to Orton, who in turn drops it to Mark Henry as he did anyway. Or perhaps Edge keeps the WHC past ER and Christian turns heel and wins the title for a short time from Edge before dropping it back to him by the end of Summer, and then Edge goes on to lose the WHC to Henry himself. Or Edge just never loses the title at all during any of 2011 past Mania before dropping it to Henry in the Summer or Fall. Either of these three scenarios seem likely.