According to this, he's still running the same routes, but defenses are backing up to guard against his speed, opening up routes underneath.
Need to Know: One more reason to like RG3 - Rich Tandler's Real Redskins
Here's the money quote from Kyle Shanahan:
“He’s been out there. He’s been doing the same stuff he’s been doing all year, but you only throw them to him when the coverage dictates it. Sometimes when you get a guy uncovered 50 yards down the field, teams tend to back up. He’s still running those same routes and stuff. Guys are backing up a little bit more and it really helps out guys underneath. He’s done a good job in a bunch of these games really scaring a lot DBs [defensive backs] and getting them out of there. It opens up stuff for people underneath and when he doesn’t, you’ve got to be willing to let it go.”