I quickly looked in the coding tasks submitted on the site that was mql5. Out of their most recent 100, 13 are for MT5. Thats 87% for MT4. A year or so back it was more like MT4, therefore MT5 is obviously gaining popularity.
I believe it would be a mistake to induce people to change from MT4 into MT5 as people naturally rebel and Metaquotes may find themselves losing market share.
I think that MT4 has been a Golden Goose to get Metaquotes and it seems absurd to Kill it, in my view.