The winner of Randy Orton vs. John Cena at TLC would be using only the WWE Title belt. As seen on RAW, new champion Orton came out with both belts. Word coming out of RAW is that eventually the champion will hold just the WWE Title belt. Orton coming out with the World Heavyweight Title belt on RAW was a last minute decision.
As latest reports come in of a rematch at WrestleMania 30, they might reveal the new belt the night after on Raw.
Back when WWE unified the tag team titles, they used both belts until they came up with the current belts now.