I think he's said that's it for the track after this Olympics. I don't think Wiggins has more than a couple of good years in him, by which point Geraint will be hitting his peak at 28.
There was a great programme about Geraint on ITV Wales the other week, one of my clubmates was interviewed about their time together in the Maindy Flyers. Sadly, ITV don't put ITV Wales programmes on ITVPlayer.