There's no Skyrim sequel coming for ages
Bethesda's VP of Marketing Pete Hines was chatting with Dualshockers at Gamescom about Fallout 4 and briefly addressed the company's other series. The bottom line it will be a 'very long time' before anyone is talking about a sequel to Skyrim.
The main reason for that is Fallout 4, which is currently on the home stretch for a November 10th 2015 release. Bethesda is committed to getting the game out in the best shape possible, and also supporting it post release with updates and DLC. As a company, they like to be able to focus on a single title completely both pre and post launch to give their audience the best possible experience.