Yes, this does sound like the kind of move that one should make if one has a solid, perennially contending team, with plenty of youth in the pipeline to step up and replace productive veterans.
I think you can see where I'm going with this...
I guess it depends on how the Dolphins view the future.
IF the dolphins feel 2013 has a real potential to be their year to win the superbowl absolutely don't trade him.
But if the Dolphins figure it is going to take until 2015+ to have a realistic shot to win the SB (time to develop Tannehill and put together other pieces of the pie along with letting Brady get closer to retirement) then it make sense to trade him for either a player or pick that will help them win the big prize.