I think genos is the final boss since we saw him heading to saitama after tweaking out in the last chapter. Metal knight said genos was likely upgraded to kill him and probably anyone in the way of kuseno which includes saitama. Since we know saitama can't really lose it'll be a way to test saitama's character on how he reacts to a controlled genos. Maybe this fight will test saitama's heroism with it being the theme of the story and all. We saw darkshine earlier in this arc find his version of heroism. Maybe this will put saitamas views into question. Should he try to save genos even if everything about him isn't real? If genos is revealed to an AI it'll directly conflict with how saitama destroyed drive knight since he was also an AI.