Long ago I promised that I wouldn't kick anyone out of my top 200 anime rankings until I had at least rewatched every ranked series. For series with lots of sequels and spinoffs, it's fine to not have rewatched everything if the core quality of the show that got it ranked in the first place has been rewatched. But shows that I've never rewatched can't be assured to be great to the point that shows I have rewatched are bumped out before them.
In a case like that, it would feel like the shows that have proven their worth were losing out to shows that never had, and it feels a bit unfair and non-objective.
Currently I've yet to rewatch six shows that fall under those circumstances: Princess Principal, Suka Suka, Imouto Sae Ireba ii, BanG Dream!, Ryuuou no Oshigoto! and Death March.
Princess Principal and Suka Suka I just haven't gotten around to yet. The other four haven't come out in blu-ray so there's not much that can be done about it even if I wanted to.
Luckily there were no great new anime franchises introduced this spring season, so it wasn't a promise I even needed to worry about, but the summer season is coming up soon. What will I do about things then?
I intend to keep my promise. Nobody new will be allowed into my rankings, even if they show great potential, until I've fairly watched and rewatched all the concerned parties. This even includes the new series that are hoping to bump out the older ones. They won't be allowed to do that until they've not only been watched but rewatched in full, which might be years from now. Which means my rankings aren't going to be adding or subtracting anybody for a long time, even if I do manage to clear out my current backlog.
Of course, if a series looks promising, I'll be sure to say so, and any good series can still hang out in the runners-up section without a problem. It's just that I won't label any series great until I've watched and rewatched the series. Right now I'm operating on the honors system, labeling stuff great and then rewatching it later to justify my initial impression. That's worked fine so far, but now that series are going to be losing their status as great from here on whenever a new great series is announced, the gravity of the situation has increased, which calls for a higher degree of self-assurance before making any moves. It would be unfair to series who have passed my test to be losing out to series who haven't, so things have to change accordingly.
If a show just stubbornly isn't coming out in blu-ray and I want to induct it into my rankings already, I might give up on the blu-ray aspect and just rewatch the tv version (which I had to do for Idolm@ster: Cinderella Girls for instance). But it's more fun in general to wait for the blu-ray version when the shows have already become hazy in memory and everything feels new again the second time around. So whether the blu-ray releases are speedy or tardy, it will still be a year or so before any new series could possibly be inducted.
With that said, what shows have potential in the coming summer season to eventually make some waves?:
First, the eternals:
Sequels to known good shows:
Shingeki no Kyojin 3
Yama no Susume 3
That gets us seven shows in the bag. How about new franchises?:
Isekai Maou to Shoukan Shoujo no Dorei Majutsu
Series worth at least checking the first episode out:
Yuragi-sou no Yuna-san
Shichisei no Subaru
Sunaharasou no Kanrinin-san
Angolmois: Genkou Kassenki
Shoujo Kageki Revue Starlight
Hyakuren no Haou to Seiyaku no Valkyria
Lord of Vermillion
I predict a season with maybe 10 shows worth watching. Overall it's going to be awful, the worst season of the year by far. I also predict that none of these shows will make my rankings even years from now, so my promise will remain a non-issue for the foreseeable future.
Of course, I'm always happy to be proven wrong. But none of the preview information of these shows gives me any confidence in them, and there isn't much hype surrounding any of these new franchises either. It's not like any of the source works have won any prizes or have millions of fans or anything. It feels like the entire industry is just going on break until the fall season begins, where all the serious shows are slated to air -- SAO, Fairy Tail, etc.
2018 is going to be a great year in anime, but no thanks to this summer. Everything is slated for autumn. It's going to be a long and painful slog.