I really don't see the point in including Shazam in a Justice League that already has Superman.
Because, even though they have similar power-sets, they are very different kinds of characters.
I'm guessing we might see Black Adam before the Shazam movie. Heck we might even see Captain Marvel (I refuse to call him Shazam) before the Shazam movie.
Yeah, in the New 52, Shazam is like Superman if you made him a selfish sociopath. So, there's that to look forward to
Seriously though, Captain Marvel and Superman were always pretty different. They're probably more different than, say, Batman and Green Arrow. Before the DC reboot, having them on a team together would have worked fine, although I don't think they were ever in a version of the Justice League together. Shazam doesn't work in the Justice League comic at all now, but mostly because he's written really badly and is about as far away from being a compelling character as he can be without making him a violent criminal.
This list of movies is interesting. If the people behind the Marvel movies were doing them, I'd be super excited. As of right now, I have reservations but I'm willing to wait and see what happens. Well, except for Shazam, all signs point to the movie using the horrible, hateful version of the character. Captain Marvel is my favorite DC hero, and I really hate the current "Shazam", so that's the one DC movie I really have no desire to see get made, at least with the current idiots in charge of the movies. But, I'd like to see these movies be good, so I'm hoping WB can surprise people and turn their movies around quality wise.