Yeah, that isn't an unexpected move. Read about his imminent release a couple of weeks ago. He's a good corner, but an oft-injured one. It would be too big a gamble (no pun intended) to take if we're expecting him to be on the field for 16 games.
There's no doubt that salary cap issues will force a LOT of good NFL starting-caliber players into free agency next week. I think both Sean Smith AND Jake Long will see a little bit of a comeuppance if they believed the gravy train was on its way.