With Airtel's 4G ramp-up, Idea is accelerating its own 4G rollout to 10 circles. Idea now has 0.7m 4G subscribers out of total 44m data users. Data usage by Idea's 4G subscribers is ~1.7x of 3G subscribers, which are at 23m.
Idea Cellular did not foresee 4G being adopted in India and hence was laid back in its approach to spend on 4G Infrastructure. Details on
Idea Cellular's Flip Flop Strategy towards 4G LTE is covered here.