This is very important. Unless they implement VoLTE, it doesn't really make sense for people with 4g handsets to stick with RCOM. At least in states like kerala where they don't have 3G network at all. Moreover, the voice clarity is below average in my place at least.
One thing I heard from one of the old employees of RCOM is that they are currently concentrating on the Aircel merger not on any network expansion. In fact he also told me that though it is projected as a merger, it's more like selling RCOMs wireless business to Aircel and most of the key positions in the company would be taken up by Aircel employees. Not sure how far this is true. But I believe it to some extend with my experience of sending a mail to RCOM appelette authority and I am yet to get an acknowledgement or response of some sort even after 3 weeks. It seems that RCOM doesn't really care about their current customers. They are busy selling their company to Aircel.