I don't necessarily think they are; the OP stated the Spotrac dude on WGR suggested it. However, I believe the Chargers are about to go through a rebuild soon, and may not be looking to pay him for a second contract coming up.
The OP stated Mike Ginnitti from Spotrac on WGR suggested The Chargers might be trade target for Mike Williams. I am not sure if he is a viable trade targer or not, but I think the Chargers may soon be going through a rebuild.