There is a statement at the start of the closing credits: "The Guardians of the Galaxy will return." Accompanying it is a scene of Groot dancing to Quill's music. The Guardians' next appearance in the MCU is in Guardians of the Galaxy Vol. 2 (2017).
There is a scene at the end of the closing credits: Tanaleer Tivan sits amongst his wrecked archives and is comforted by Cosmo... and mocked by Howard the Duck. The scene is followed with credits for Howard's creators.