I really don't know how they legalize or i-legalize such thing as bitcoin because you are using it with your own internet and computer hardware maybe they just not supporting it before but every citizen of India can use it no matter what happens unless their government issue a criminal liabilities in using bitcoin.
Indeed it won't matter if Indian finance ministry applies any kind of regulations unless its illegal use is amended in the law. I don't think by any chance they will do that because bitcoin is very valuable paradigm of this era and India is already taking giant leaps through economic development. Plus India is biggest populated country which gives bigger support to the economics market and forms the back bond for it.