Based on the recent numbers from GSMA it seems that over 50 % of the world population is now in a reach of 4G services. The number of VoLTE deployments in 2016 (May) is already close to the number of all the deployments for the year 2015.
For RCS we can still see some new deployments. However right now the RCS is a bit stagnating.
Sure, one thing is the number of deployments, and the other is the number of subscribers. But clearly we can see that telco engineers have a lot of work (and stress as well :-)). Also the prognosis, that with the 4th Generation all the communication will move to OTTs, were a way too optimistic/pessimistic (depends on angle). The statistics along with some more detail information can be found on GSMA pages.