I just pulled the camper home in my sig this weekend, with the truck in my sig. The camper weighed 6300lbs according to the sticker. It was empty.
Granted, it's a small sample, at about 600 miles, but I got 8.5mpg. That's at 65mph, and with a pretty solid wind, head on, or on the quarter, for about half that drive, and rolling hills for roughly half. Under better conditions, I'd hope for closer to 9mpg. Maybe a bit more with a little luck or a little less speed. Doubt I'll ever see 10 though unless we move somewhere flat.