They just started adding power-up, after power-up, after power-up. So far, the Sharingan can:
-Predict someone's movements
-See through illusions
-See an opponent's chakra
-Make an individual experience whatever the user wants them to (being cut, burned, etc....) for 72 hours, although only a few seconds will have passed in reality.
-Can create a dimensional rift and send things to other dimensions
-Some other shit I can't remember.
And in one of the latest chapters, Sasuke obtained yet ANOTHER form of the Sharingan, but we don't know what it does yet.