Word has it that the solo Flash movie will be taking its main inspiration from The Flashpoint Paradox, and a lot of people got excited because it's one of the greatest stories from DC comics. What's a bummer is, it looks like the film will be dropping 2 major plot elements from the original story.
According to Heroic Hollywood, The Flash won't be featuring Thomas Wayne's Batman as well as the Amazon/Atlantean War. By the looks of it, the Batman role will be filled in by Michael Keaton, and the only thing that's going to be borrowed from Flashpoint is Barry messing up the timeline.
In the alternate Flashpoint timeline, it was Bruce Wayne that was murdered in Crime Alley, forcing his father Thomas to become the Batman instead. The world had also been torn apart because of a war between the Amazons and Atlanteans; I don't want to get into details, but Wonder Woman beheads Aquaman's wife Mera and wears Mera's crown like a sick trophy, and Aquaman puts Europe underwater—it's crazy.
While a lot of fans see this is a huge con to the Flash movie, I think this leaves a lot of room open for a sequel. While we're surely not getting Darkseid now, I'd prefer we got a Justice League movie centered on Flashpoint. I mean, it includes everyone from Wonder Woman to Superman, and if Ben Affleck isn't coming back, we have Jeffrey Dean Morgan to play Thomas Wayne anyway.
Then again, these are all just rumors, for now, hopefully we get more details when DC FanDome takes place on Aug. 22.