Dragon Age: Inquisition may see the return of Dragon Age: Origins party member Alistair in some capacity.
There's no guarantee Valentine is recording for Inquisition, as opposed to a side project or perhaps even Dragon Age: Keep, the bridging system for those who can't import their save files.
Even should the recording be confirmed for Inquisition, it's possible Alistair provides a narration or makes a cameo rather than a longer appearance.
Valentine's character, Alistair, was a primary party member in Dragon Age: Origins, and has featured prominently in several comic book series. According to the canon set by the comics, the cheeky ginger is king of Ferelden in addition to his role as a Grey Warden. Depending on your save state, Alistair can make a brief appearance in Dragon Age 2.
Dragon Age: Inquisition is expected in Northern Autumn on PC, PlayStation 3, PS4, Xbox 360 and Xbox One.