[Nursie]

Sure, those are some client implementations, not all, people are free to interact with the network in all sorts of ways. Servers are also free to not include transactions that don't have enough fee for them.

I'm sure when the time comes something will be worked out, but it is most definitely voluntary rather than an enforced feature. Hell, do a quick google search for "Bitcoin no fees" and you'll find thousands of BTC supporters shouting about how it's so awesome as a payment method because there are no fees!