I love how people say "I will!"
For starters, most won't. These are people who tend to be ideological and naive kids who probably still have their parents paying their bills. Or they don't really fully understand what the implications are. Also, subscription models have proven to be poor solutions and don't work very well at best, and at worst, completely fail taking the website with it.
Another thing, what about poor people? We talk about how people "are happy to pay for content they like!" Only, there are going to be a massive amount of people who simply can't afford to use the internet that way. If the entire internet turned into "pay as you go", the poor & working class are screwed. They're the ones who are going to be the hardest hit. Not just poor people in the U.S but what about all that traffic from other countries? And there is a lot of it... That's a lot of people who used to be able to keep up with current events, study science, math, history (educate themselves), chat on forums, make new friends, play games who now can't, because they can't afford it. To me, that's a shame. A travesty even if you take into account the educational aspect.
I feel like the people who push for the paywall & a la carte type solutions don't really consider the full implications of their suggestions. I mean, I thought about it myself the last time it came up on hackernews for weeks, no, months and I still have no clue how the internet would evolve as a result. And what little I did conclude wasn't good. Yet these people seem to be so certain...