During the WWDC 2010 keynote Steve Jobs announced the availablity of iPhone 4 around the world to be completed in 4 phases. Phase II ends on July 30th & Phase III sometime in August. In September during the final phase iPhone 4 will be available in 88 countries.
Airtel is the most popular network provider in India and they might roll out the new 3G services around October so the launch of iPhone 4 around that time might be good way for them to promote new data plans and services.
Bharti Airtel CEO Sanjay Kapoor, during a CII industry conference confirmed that the company will launch the iPhone 4 in India soon:
We are working with Apple. Hopefully, we will launch it in the September-October timeframe,
In India iPhone 3GS 16 GB model is currently available for Rs 35,500 ($750) and 32GB model for Rs 41,500 ($877) and it is interesting to note that the phone is still sold locked to the network provider and cannot be used with other networks. While in UK one can buy a contract free phone for almost the same price.