Bandwidth costs money, and if they wouldn't charge a subscription fee from their users, they would have lost the money from their sales in only a few years. It's not like people are going to stop playing after that anyway, so they'll end up losing money if they don't charge anything.

So yes, I'm almost convinced that they will charge for it.

"Stephen Wolfram is the creator of Mathematica and is widely regarded as the most important innovator in scientific and technical computing today." - Stephen Wolfram