This is a very smart move. I think the IAF is thinking like me

. For making it economically viable they are going for a common replacement of Avros and the An-32s. But they are smarter even.
1. Upgrading the Avros for now allows an uninterrupted assembly line producing 145-180 planes from 2020-2021 onwards.
2. In case of delays, they have a padding of 2-3 years.
4. Upgrading the Avros first and then building the complete plane is an easier learning curve.
Here is the layman timeline in my head.
1. Finalize the private agency and extent of upgrades by 2014. Upgrade the aircrafts by 2017.
2. Identify a common plane to replace the Avros and An-32s (combined order of around 200 aircrafts) by 2017.
3. First 16 aircrafts come from the OEM by 2020. Aircrafts start rolling off the Indian assembly line by 2020
5. Indian made aircrafts start active duty from 2021 replacing the Avros first and then the An-32s starting 2025.