Since the general consensus is the assumption Miami will not keep four Qb's on the roster I guess you have to break it down in terms of value.
The second assumption is no one with the first name of Chad is going to get traded that leaves the following question:
What can you get in return for what is left and what do you have invested?
a) With White you have a second round pick invested and no hope of retrieving that pick but you more then likely can get a player of equal talent.
b) With Thigpen you have a fifth round pick invested and good chance of getting that pick back or a player of equal talent with the outside shot at a higher pick or higher talented player if you find a team that is desperate.
It wouldn't surprise me if Thigpen is traded based on the above conditions just by the simple fact that return on investment dictates that Thigpen has more curb appeal then White and the chance to offer a player that can fill a need or a pick that returns the same amount of value invested in said player.
I guess this saga will unfold with the passing of time and maybe we are all wrong and Penny gets the boot or Miami keeps four QB's.
You don't look at ROI when selling something, only when buying it. Once you've bought something its a sunk cost.
For example, I buy two cars:
A) Dodge Neon - $50k (I've over paid for this car because it had a cool paint job, i.e. Pat White) This car has always had a bad engine, lack of power, and burns oil; probably going to die.
B) Ford Fusion - $2k (I got a steal on this car at police auction, potentially worth more than I paid) This car runs ok, but still isn't a Ferrari.
If I could sell both for $5k each, based on your logic I should sell the Fusion because I paid more for the Neon? This leaves me with a busted car that I probably should still get rid of.
They should ignore the sunk cost of the draft pick and determine which is better to have on the roster.