Are Japanese audiences getting genre fatigue with battle shonen?
Considering Jump hasn't given up its "Hard Work, Friendship, Victory" brand, they're not getting fatigue. It they are tired, they probably stop reading Jump altogether after a while though in recent years even 40 year olds continue reading jump. There are also people that don't want mangaka to try new things and basically want mangaka to write stories that stick to shounen formula. One guy called Heroaca's current arc trash and said Shonen manga should basically be the MC growing stronger and defeat his opponents left and right have plot points that end with the reader feeling refreshed.
I'd say lukewarm feeling in japan is still considerable better then the cold shoulder that some people in the west seem to be giving it. It's still good that the sales are rising so long as that is happening then I'd consider the anime a success, I can see Shounen Jump thinking that way as long as it's sales still increase then its a success. Other then volumes does black clover have any other merchandise out yet?
Yeah I know it isn't the only thing that factors into it getting an anime, but in my opinion it's one of the factor that is held in a pretty high regard. I think the reason that Sumou hasn't gotten an anime, as of yet, is that the two of the three factors that could lead to an anime aren't being met those being: first popularity as a title which it has, second merchandising possibilities outside of the manga volumes, and third positive focus group thoughts on the idea of an anime. It has the popularity as a shounen jump title that sells fairly well as well as ranks pretty good, but outside of volumes what type of merchandise are people willing to buy in regards to Sumou (toys, apperral?) also the focus group of people who've never read the manga's thoughts on Sumou's premise would it be popular with them also?
BC has an upcoming card arcade game and Ichiban Kuji's are either ongoing right now or are set to start next month. We don't get any sales figures for the arcade game and Ichiban Kuji, though you will find people on twitter saying the Ichiban Kuji is sold out. I have yet to see that though for BC.
Merchandise-wise, toys and the like aren't really put out first. Most series start with stuff like Key chains, Stickers, Prints and the like. Heroaca to this day still doesn't have an All Might figure, the type you see of Superman, even though there are indications that kids also buy merchandise and play the arcade game. They still keep putting out new acrylic stands, prints and gachas, which sell well, but no figures aside from the Deku and Bakugou Nendoroids and Figmas. If Sumou catches on, merchandising is not a problem as even Tokyo Ghoul has merchandise.
I don't really understand your third factor though. The point of the anime is to get it out into the world, outside of people that don't read the series or maybe manga in general and make them interested in Sumou. Seeing that its lasted this long, it has every chance to be popular.
