Yes, if the Dolphins are considering a trade, it is really in their best interests that he sit out.Teams around the league know his injury history, just as they know how effective he is when he is on the field. I think they are all smart enough to realize that the present ankle injury is nothing more than a ploy to avoid the possibility of a real injury so he can be traded if it comes down to the Dolphins and his agent not being able to resolve his present contract issues.
Remember, he will have to pass a physical with any team he is traded to before the trade becomes official. So whether he plays for the Dolphins or sits out because of his supposed ankle injury is really irrelevant when determining what his value is in a trade.
In the event that he isn't traded, he doesn't really need many practice reps to step in, and perform his specific role at a high level.