According to a source, people within creative wanted him out of the title picture immediately after The Survivor Series due to the concern of him continually failing to win the belt while chasing it. It is an issue that creative and the McMahons are very well aware of, however the decision was made to go with Ryback - Punk at TLC anyway.
The current plan is to obviously have Punk defend the WWE Championship at The Royal Rumble against The Rock. It's unlikely that Ryback would leave TLC with the title unless WWE decided to do the title change, only for Punk to regain it shortly thereafter.
Another source noted that Ryback has gotten over with the fans better than many within the company expected, so one would expect him to be booked strongly if he loses to Punk at the pay-per-view. The Wrestling Observer recently reported that one scenario for the finish of the match was to have The Shield interfere, resulting in Ryback putting each member of the group through a table while Punk climbs a ladder to snatch the belt and win the match.