Many companies offer free services to individuals, but charge corporate users for support (example: Red Hat Linux). Could it be that?
Otherwise, it is fairly common practise to offer free services to build a critical amass of users. Once acquired, you can start charging them, although you will probably lose many users. Or, you could introduce premium services, after having let them use the free stuff for long enough to get hooked. Or, even just start advertising.
Another alternative is to grow something so big and attractive that it is bought out by Google, FaceBook, Amazon, Twitter, etc. I remember 20 years ago, when Microsoft paid two college kids over $400 million to buy Hotmail.
In short, we can’t really know what they plan unless they say so publicly. Did you Google? Maybe there is something in the trade press? Failing that, all you can do is wait and see what happens.
[Update] And don't forget - if you are not paying for a service, then you are the product. No doubt they collect - and sell - lots of user data.