As of now, the GVK consortium has taken over the running of the airport from AAI. Things like passenger handling, amenities, etc are being handled by them. AAI is giving them valuable experience on running the airport.
As far as the actual physical work of re-modelling the airport is concerned, it will take some time. As of now, the second half of Terminal 1B is ready and will be opened up soon. This will double the number of check-in terminals at the terminal. Next up is the arrivals area of 1B as currently all arrivals are being handled by 1A.