1. Improve the quality of the service. They make millions and millions of dollars of PS+ and yet PSN servers seem even worse than they were on PS3.
2. Offer better games. I haven't subscribed in months, maybe even a year, because the games offered have imho been quite assy. They even reduced the number of games but still kept offering poop.
That's about it. A higher tier service that combines both, similar to what Microsoft does now with GP Ultimate, would be nice but it also seems like a logical step Sony will take.