First of all, lots of people on the forums and elsewhere have this notion that carriers are a bad unit...let me tell you, as will other Terrans, carriers are one of the strongest units in the game right now.
The strategy that lots of top level protoss are using in pvt on ladder, mostly in upper tier masters tho, is playing a standard game with the goal of mass cannon turtling with the khadayarin amulet.
The idea is, once they reach this point, they are ahead in expansions from mid-game pressure on you with collosus/gateway units, and suddenly they have expansions that anywhere on the map are defended by cannons+ templar warp-ins + army movement.
This is not theorycraft - this is what people are actually doing. I will provide one replay from a game earlier, as well as other losses to the same strategy when I look through my replay folder later, as i'm sure I angrily named them
So on with what happens...after they have the amulet upgrade for templar, they start to literally mass carriers + templars + collosus/gateway units as they see fit for, with the eventual inclusion of a mothership.
Bio does not counter this strategy directly, because carriers are air units...and templar storm is going to kill the only viable counter to pure carriers - mass 3/3 marines to kill interceptors.
Mech works in the sense that you're less vulnerable to templars, but it does not work in the sense that you can never attack protoss if you go heavy tank mech and they turtle into carriers...as over half your army will be tanks/hellions and you'll suddenly have to do a massive tech switch to the only available counter carrier measure - mass vikings, which also is countered by templars and vortex.
All right, so we've narrowed that down. What has worked for me one time versus this strategy, was a bio mech mix of mass marines, mass tanks, and vikings + ghosts which turned out into an insane game of emping templars and then hitting expansions with tanks/marine, with marines killing the interceptors, and vikings killing the carriers.
The other more viable strategy I believe, and I've also seen drewbie use it once versus a turtle templar/carrier player on his stream, was what I just tried in a game which was standard bio/viking, into mass BCS/ghosts. This I think would be the main counter, but I am wondering what other Terrans high up on the ladder are doing.
How should Terran go about fighting mass carrier + templar? Here is the replay of a recent game where I played versus this strategy (and lost), and I went for mass 3/3 BCS with ghosts.
You'll notice the protoss almost never commits to an attack, and instead gets a few collosus and immediately goes to the amulet upgrade into the strategy I have just described.
Any tips or ideas on what I could have done better are appreciated, as I don't think the strategy itself is imbalanced, but you just have to be really on the ball and get into the BC lategame to beat carrier/templars.