There is some real danger of them losing sight of this actually being a Superman movie, not a Batman or Justice League movie.
It would be kinda cool if Superman's arrival brought Batman out of the shadows and empowered other heroes to start their careers. Maybe just news reports about the Flash, WW, etc...but very little screen time or closeups of their exploits.
This movie should only bring in Batman as a mentor/adversary/ally. Only by joining forces can Superman and Batman defeat the evil _____. That in turn inspires them to seek out these other emerging heroes...blah, blah, blah. Then they can show up in cameos in those other character's movies over the next 3-5 years before a proper JLA movie brings them all together officially.
But if the 2015 movie turns into a superhero convention without laying the necessary groundwork, it'll be a wasted opportunity.