In August-October 2015 Vodafone India released statement in major indian newspaper that it would be launching 4G service in Mumbai, Delhi, Kolkata, Bengaluru and Kochi by 2015 calender year end. However only Kochi got 4G out of these 5 cities which much smaller than other 4 cities. For time being I can’t even see test signal of 4G in Delhi for now and neither it is reported by resident of any other cities mentioned. Mumbai being major one where Vodafone is leader and has enough spectrum to launch without making any major changes to its 2G n 3G network.

From what I have seen from days of take over from Hutch to Vodafone that network upgradation is delayed a lot. The pace of network rollout in comparison subscriber growth is too slow in current day Vodafone compared to previous Hutch and infact that day would be not far when Vodafone would lose its 2nd position to Idea which already is very strong in rural areas and catching on in urban cities too where vodafone has stronghold currently.
Good luck Vodafone!