No no, no fees, not yet anyway.
Honestly, I doubt they would suddenly demand a fee 2 years or so down the road. The backlash would be severe, to say the least. But they could introduce a "new" system (ie. the same but with payments) for new titles and drop support for the old ones.
They promised a take-of-the ball-and-chain patch if they ever take the servers down, but they never said they wouldn't charge for such a patch (but again, the backlash would be severe).
Scary thoughts, let's hope the future is brighter than that.
