The way i see it the after the disaster that was Green Lantern the Flash movie, which seemed to be next in line, won't be happening any time soon. After all, the Flash project that is in production right now has the same people behind it that did GL. Berlanti, Green and Guggenheim are writing it and Geoff Johns, who seemingly played a big role in the GL production, is also heavily involved.
And besides, just like with Wonder Woman, they've been unscuesesfully trying to get the movie off the ground for a very long time. There have been 5 screenwriter (teams) on the project in 6 years, which kinda proves that nobody seems to be able to come up with something the studio likes enough to actually greenlight it. Back in 2004 they had Goyer, who's approach seemed like the most promising to me. Then they gave it to Shawn Levy, before replacing him with David Dobkin and Craig Wright, who were hired to write the movie as a JL:M spin off. After that went nowhere, Dan Mazeau was supposed to write a script based on a treatment by Geoff Johns. Much like with Johns' Captain Marvel movie, we never heard anything about it again until they announced the Green Lantern Writing team was now also doing The Flash.
So after GL failed the way it did i doubt they've gained confidence in characters they obviously didn't have enough confidence to greenlight a movie before.
As i've said before, from my point of view, the best thing to do next for DC Entertainemnt would be to go with the JLA flick and continue form there. Since it features their two big guns, Superman and Batman, it's a much saver bet than anything else they can do right now. And it could also built some new momentum for the other character that could lead into some solo franchises spinning out of it.
Personally, i never got that single minded way of thinking some fanboys seem to have. These movies don't need to get bigger and bigger with the biggest one of them (the team up flick) coming last. The way a studio looks at it, there is no endpoint to these plans anyway. Just look at what Marvel is planning after Avengers. They won't continue with flicks like Secret Wars or anything like that, they will do Iron Man 3, which seemingly will be on a much smaller scale storywise than what came before.
And as for the need to introduce these characters in individual movies before the team up flick... i think that's very overrated and leads to exactly what we're seeing right now... pretty much every movie following the same boring (origin) formula. There are so much things you can do with these comic book proporties that would translate into much more interesting movies that really don't need the audiance to know every detail of the origin story of every character the movies features.