A long time ago, I mentioned on the Berklist that I had an idea that Ars was stronger because we had played out the easy stories, and you asked me to elaborate, but I never did. Now seems a good time, because it colours my answer and I've had time to think the idea through.
It struck me, in the Amber community, that the game was stuck, because it only ever published a few supplements, and so by the time that we got the official version of obvious stories (like "Brand Returns", for those who have played the game) the fanbase had moved far on from that point, and completed so many fascinating experiments that the offical ones seemed neophytic. Brand returns? We have -all- done Brand Returns, and yet new people to the game were not being given the benefit of thousands of hours of play. They were starting from the same first principles as the rest of us, and so, every new player invented "Brand Returns".
Similarly in Ars, we have all done some of the obvious stories. Druids coming back and so on. In Ars 5th, it was time to move on. Time to find the stories which were only possible because we, as a community, had already worked through the simple stories. Time to say to new players. "Here are some of the low-lying fruit we have already picked. Now, time to show you some of the stuff we discovered afterwards!"
In any books that repeat a theme we have seen before, I hope to see the same thing. I hope we will see nods to the old and obvious, and to the old and difficult that looks obvious now because people told you about it back then. I also hope to see what people have been doing since they digested what was revolutionary back in the day, but is obvious now.
What has our community learned about hedge magic since "Hedge Magic", or about faeries since "Faeries"? I think there's been a lot. For example, "Covenants" was a lot different to "Covenants" and "City and Guild" was a lot different to "Mythic Seas".
I hope to see how far we have come. I hope to see us build on the foundations the community has laid down.