This is very likely to happen next year. They didn't pay so much for bagging the digital rights to give it away for free even though they get the Advertisement revenue. Viacom18 wanted to test the waters with the free streaming and give the people a taste of the services so that next season onwards when they charge, people are willing to pay.
It is highly possible that Jio subscribers may get the jio cinema app subscription complementary with the unlimited mobile and broadband plans and the subscribers of other operators may want to switch to Jio for the same.