Yes, and it was wonderful. I saw Die Walkure which they unveiled before the full Ring and then the Ring itself. I didn't agree with all of Zambello's choices, but hers is thoughtful and vibrant direction, and she's always rethinking things and adjusting and clarifying.
The cast members who are returning are three wonderful tenors: Jovanovich, who sang a superb Siegmund in the preview Die Walkure and in the 2011 Ring, Margita as Loge, and Cangelosi as Mime (The latter two just about stole the show in Das Rheingold and Siegfried), the fine Citro and Miller. (Citro was Freia and Gutrune in 2011; the 2018 website doesn't list anyone for Freia). Also Andrea Silvestrelli (Hagen and Fasolt), whom I don't like, but he was in the young artists' program in San Francisco, and you can't have everything.
Seattle was lucky to have witnessed Grimsley's first Wotan/Wanderer in 2005; he also sang in the 2009 and 2013 cycles and his portray got better and better as he fine-tuned the role. I saw the first and third Seattle cycles in 2009, and he and Stephanie Blythe (Fricka) didn't simply repeat their first cycle performances in the third: they were more in the moment. Jamie Barton sounded wonderful as Fricka in some excerpts I heard from Houston. I'll miss Gordon Hawkins as Alberich, but am interested in seeing what Struckmann will do with it. Herlitzius I've only heard over the radio, but I'm really looking forward to her Brunnhilde. I don't know Brenna at all, but I've read some excellent reviews of him, and I'm guessing he'll be stronger than Storey was.
In my opinion, this is about as good an all-around cast as it gets now. The orchestra sounded great under Runnicles; I saw the second cycle, IIRC; any issues with the orchestra raised in first cycle reviews must have been ironed out.
In addition to the Ring, there are a series of Wagner-related presentations:
https://sfopera.com/ring/planyourring/ring-festival/
The Symposium on Thursday and the Forum on Saturday (followed by the movie) add to the full immersive experience: in these presented at the Toronto Ring that opened the Four Seasons Centre, I learned what a Ring Head is from the horses' mouths. Your son might be amused as people who recognize each other from any number of Rings they've seen around the world brag about who's seen more, the best, the rare substitution, etc. The speakers for each Saturday forum are currently listed; the Symposium guests are not yet listed, but they tend to be a range of performers/designers/directors, producers, and Ring scholars.
When I went in 2011, I splurged on Dress Circle tickets. Not this time, because they are running Operavision for all three Rings in the Balcony. For me, this is the best of all possible worlds: you get to hear it live, but if you look to the side, you get the "Live in HD" close-ups projected on screens, with subtitles. (The titles in the main house are projected at the sides of the proscenium.)
San Francisco is also fantastic in the summer, and there are two opportunities mid-cycle for overnight trips to Napa or day trips.