According to Afaqs’ Telecom Yatra, Vodafone Essar has announced that it will launch the iPhone 4 in the “coming months”. This information by itself doesn’t mean an exclusive Vodafone launch, but simply that no other carrier [read Airtel] has reportedly announced it yet. Apple itself had announced three waves of retail release, with the first wave being 5 countries including the US in June, the second consisting of 24 countries in August, and the third for 40 more countries in September. It’s quite safe to assume that the third wave is the one that will include India, but like the iPad’s delayed international release, the iPhone 4 too might be further delayed.
In any case, it’s never too early to figure out how to make your normal SIM into a Micro SIM, without waiting for the carrier’s solution. You might consider the CutMySIM device, which is $25 till July – when its price will go up.