The reason WWE Superstar Christian has yet to return to action is because he has yet to be cleared by doctorsfrom the concussion he suffered a couple of months ago. The current expectation is that Christian will be back on WWE television by early December.
Source: http://www.sescoops.com/update-christian-will-return-wwe-tv-mcmahon-talks-raw/
Source: http://www.sescoops.com/update-christian-will-return-wwe-tv-mcmahon-talks-raw/