I don't think WB really has an idea what they're doing, and if talks of one day crossing over with characters like Gadot's Wonder Woman or Momoa's Aquaman weren't present at the start of negotiations with Matt/Robert, then it'd be a helluva hurdle to cross in order to get them on board.
I think, at least from a story perspective, the most obvious thing to do is have the upcoming Flash movie hit a select restart on the universe, a la the actually flashpoint comic, or have a Rebirth esque mish-mash of old an new elements folded into one. But considering that Ezra Miller just assaulted a fan and that movie is on it's 20th director, really doubt it's gonna see the light of day (or will have any old DCEU connections).
I doubt Matt/Robert would agree to anything without a plan and as nice as it would be, I really doubt Flashpoint is part of a plan at this rate.