Well, it seems like newly signed Gibril Wilson will indeed be moving to free safety.
That's because the Dolphins were able to re-sign SS Yeremiah Bell to a 4-year contract worth $20 million, $10 million of which is guaranteed.
According to Armando Salguero, the team told Bell that he will continue to play SS. It will be interesting to see then how active Wilson will be in run support, his obvious strength, since the free safety is generally in coverage a bit more than the strong safety. That was particularly true with Miami last year, as Bell seemed to live in the box for much of the time.
I think retaining Bell is a smart move though, and Miami shouldn't have to worry about it's deep secondary for a few years (although, it'd be nice to get a late-round pick in the fold to start developing now).
This move probably means the team will not be trying to re-sign Renaldo Hill, unless he comes very very cheaply.