Source: The Wrestling Observer Newsletter
While there have been rumors that John Cena will fight Brock Lesnar at TLC in December, the plan in WWE is still for the title fight to happen at the Royal Rumble in January. Cena won the right to fight Lesnar at Hell in a Cell, and with Royal Rumble not until January, rumors began that WWE may do Cena/Brock earlier, but right now the plan remains to have the match at the Rumble.
WWE has been advertising Roman Reigns for December live events but it currently seems like Reigns may not be back until after the Royal Rumble.
WWE’s plan is reportedly still for Lesnar to retain against Cena at the Rumble then fight Reigns at Wrestlemania 31.