From what Clayton and Mortenson have said, it sounds like the Dolphins really want to showcase Ricky once he's back so that they can ship him out in trade whether it be this season or next. I'd wager at most the Dolphins would be on the hook for Ricky no more than this year.
Your right, they might be able to show case him during the preseason as he only suspended during the regular season.
Here more information about ricky williams in training camp.
Only a few guys really interacted with Ricky during the practice. It seemed like he was a little bit of an outsider, but that should be expected. Nobody really knows what to say or how to treat him One memorable sight: when the team broke for a water break, the players headed to the new covering on the middle of the field -- everybody except Ricky. He was the jersey walking against the current and wound up drinking his water next to strength coach John Gamble a good 10 yards from the rest of the players. Weird sight.