I suspect that for free content, we can look forward to ever more product placement and sponsored material, i.e., ads you can’t conveniently skip/ignore instead of standalone ads that are more easily blocked. It's been working (for sufficiently generous values of “working”) that way with TV and films for a while.
Personally, I’d rather see more effective forms of paying directly and not compromise the integrity of the content, but then I’m the guy who still buys box sets of spinning discs to enjoy my favourite shows uninterrupted and legally instead of either watching the ad-ridden ones on TV or pirating them on-line, so I guess I’m probably in a minority these days.
Given that we’ve yet to solve the micropayments problem, and even if we did it’s not entirely clear how well it would work, I wonder whether the most promising avenue might be some sort of collective subscription scheme. Smaller (or not) sites could join a collective programme that includes a lot of different sites aimed at similar audiences, there would effectively be a paywall but paid through a single centralised subscription rather than every individual site so much of the time users wouldn’t actually see it, and then some sort of simple marker that indicates you’re a subscriber and gets you in would also let the scheme track which sites were getting the most views and adjust payments in some reasonable way proportionate to value.
Some of the most successful on-line business models of recent times, other than ad-based and direct payment, seem to have been the library-style services like Netflix and Spotify, so I could believe this sort of collective subscription scheme could work if anyone had enough resources to get it up to a useful number of publishers and subscribers to be credible quickly enough. It feels like a balance of convenience and commercial viability that might actually work to me.
A significant problem might be that the umbrella schemes wind up taking a huge chunk of the revenue for themselves instead of passing it on to the real content providers, since the whole model depends on having a small enough number of schemes to be manageable for customers and that implies a degree of consolidation. Then again, we have a similar problem with big ad networks and with other types of middleman site today, so I’m not sure it would necessarily be any worse and at least very successful sites could still go their own way if they were valuable enough to their users so there would always be some inherent competition for any umbrella scheme.