With bare minimum exposure to the ideas via Free Basics, people will be able to imagine what else is out there. It becomes "Google is like when you type words into the search box on facebook, except you get more results and they're more relevant." I would imagine that once exposed to even a limited version of the internet, people will quickly demand unrestricted access from their local government. But they have to know what they don't have before they can ask for it.
If this is all an Evil Plan by Mark Zuckerberg to set up an internet monopoly in India, then it's a very stupid plan. Facebook is a communication platform. People will use it to communicate with people who have normal internet, and will no doubt hear about all the things that they don't have access to. It's only a matter of time before "Free Basics" becomes "Low Cost Government Internet Access For All".
For many people from my generation, AOL was the internet. It was all we knew. But eventually we figured out that there was more out there, and the people of India are capable of doing that as well. There are hackers in every culture, at every social strata. If you give them an inch, they'll turn it into a mile or more. Free Basics isn't perfect, but for many people it's better than nothing.