Russell Crowe who played Superman’s father Jor-El in MoS wasn’t cast for BvS but in talks with Digital Spy, he said that more movies were to be made featuring Superman alone,
I think once they made decision because originally , I could be completely wrong, there was a number of Superman movies. But I think they made the decision to jump past those and go to the idea of Batman and Superman in the same film. So, no, I didn’t have a any discussions about that.
Although it isn’t a full-proof statement but if WB had the idea of making more Superman Solo movies then there are pure possibilities of that to happen. Even though Russell Crowe will definitely not be seen as Jor-El if this happens.
DC fans would always say a big yes to any character but Superman and Batman are two special superheroes who are given footage from time to time. Now as Ben Affleck is writing the two solo Batman movies it wouldn’t be fair for Henry Cavill to not have any solo superman movies.
Another way to look at it is that Warner Bros would have to adjust in their really tight schedule and what we will have between now and 2020 would all be done really quick.