Well, before worrying, shouldn't we just wait and see? Maybe if Sanada loses, Konomi sensei will suddenly intro the Real Final Bosses (as nonsensical as this might be.... I don't think at this point Fudomine can be the Final Bosses, and Yamabuki is just too boring)

(You don't have to worry. Nothing happened in the Midoriyama ones except for some slight Nanjiroh character development. Basically Seigaku smashed them. I don't know if there's much hope left for Yamabuki without Akutsu, seeing that battles also seem to be fought on interesting-ness as well as actual tennis skill. Unlucky Sengoku can only do so much. :P )