On this infographic you can see potential evolution for Russian PAK-FA T-50 stealth multi-role fighter fifth generation, which will receive code Su-50, when production line starts serial production. Plan for serial production was on January 2016, and will fly under flags of Russia, South Korea, India and Iran.
There are already 5 prototypes.
Sukhoi wants to start producing of special version for Indian Air Force (IAF), which will gets code Su-50E.
If ever South Korean choose to buy Su-50 as their new fighter, they will getting version with local avionics, and jet will get code Su-50EK.
Su-50E have chance to get brother twin seat version co-developed with India for IAF around 2020. year.
In the same year, Sukhoi plans to share with the world Su-55-FGFAM, modernized version of twin seater.
At the end, around 2022. year Iranians are planning to get their Su-50ES version (if ever)