Can you ever see a world where the majority of anime fans pay for it? What would be the ideal way for that to happen?

No, because some people have this incredibly entitled mindset where they think they deserve to get anything digital for free forever, and thus they would never, ever pay for it.
But those are basically lost causes who wouldn't pay even if you killed piracy, so we can pretty much ignore them. As for how to win everyone else over, the key to that would be to beat the illegal options in quality, speed, service and availability. Right now the only thing where legal options beat the illegal ones hands-down is speed. Service-wise they do beat illegal options in many areas (such as availability on various platforms, easier for technologically illiterate people), but you shouldn't sneeze at the convenience of an RSS feed torrent setup either. Quality-wise the legal options have always dragged behind the illegal ones, which I find terribly unfortunate considering the legal entities get access to better sources than the people doing things illegally (really, if the world was right and just, technological progress would first happen with digital distribution of files playable on powerful computers - we could already have 4K video in common use today if Big Media didn't hate the general computer). And then there's the matter of availability, which can be boiled down to "legal options have region locking, illegal ones don't", which pretty much says it all, doesn't it.
Here's another way to look at it: I would generally say that if someone consistently enjoys the products a service puts out, they should really show their support for the service and pay for it instead of pirating - but only if paying for it gives you the same or a better experience than pirating. So with that, let's consider someone who only watches anime with HorribleSubs' 1080p CR rips. To get a similar experience by buying a CR subscription:
- The person should live in the United States (where CR has the most amount of content available)
- They should have a fast enough internet connection to stream CR's 1080p video without buffering pauses (you don't have to worry about that when you download the whole file beforehand)
- They shouldn't be using madVR debanding or any other postprocessing that is only really possible on local playback
And it's really the same thing with all legal options for anime right now - there's just way too many caveats for me to unequivocally recommend paying for them even for the people who are satisfied with the quality they put out.
It's really a sad world of legal media digital distribution we live in.

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