Not yet. Give it some time though. I'm sure someone will ask for it sooner or later.
People wanted dual specs in the past, now tri-specs. Soon it will be Quad Specs, Penta Specs etc. Then, when we have all the combinations we could think of ever needing, we want it to be even easier to switch between them, even in combat, because of some arbitrary reason, maybe a boss fight requires 3 tanks in phase 1, but only 1 in phase 2; "Would be nice to switch to DPS in combat, else I'm useless half the fight!".
See where I'm going? It never ends until you have all the possibilities at the click of a button, and without moving an inch.
You might be able to get the same thing by visiting a trainer, however, once there, you have to choose which is good thing in my opinion. Let there at least be something left that requires you to move somewhere.
As a matter of fact:
See? Didn't take long
Learn to live with the fact that you have to choose sometimes. Else, what's next? We get to have all Primary Proffs as well? Sure would be nice. Never have to pay obscure amounts of gold for craftable things like gems, enchants etc.