What are you talking about?
Man of Steel and the Batman reboot could be part of a shared universe if WB wants.
Nolan will only be a producer of both films... and frankly I think Nolan is just generously giving WB his name to ****e out.
And WB should do that. Even if Nolan has said that his Batman stands alone, they should convince him otherwise for the next phase. He's had a trilogy under his belt anyway.
If they don't make those two part of the shared universe, they'll have to start again from scratch, and that would take years. Even if the Man of Steel and The Dark Knight franchises haven't been built up as being part of a shared universe, that doesn't mean that WB can't change their game plan.
For that matter, they should also just use the Green Lantern movie and actor that they already have instead of getting a new one. I think that, once they see GL as part of this bigger team, audiences might be a little more forgiving of the GL movie and view it in a new light. Or if not a new light, then at least he'll already be out there and they can tweak his character just as Joss Whedon has done for Black Widow and even Hulk (which, although uses a different actor, is following on from TIH).
If WB use Man of Steel, The Dark Knight and the Green Lantern, then they've already got three under their belt, and they can just launch other movies like Wonder Woman and the Flash, or launch them after a JL movie comes out.
But if there's a complete reboot of those franchises, that means we have to wait for the current Man of Steel franchise to run its course, which will be years away for a Justice League movie.