User blog comment:ItzAdreen/Ezra Miller will be the Flash in the upcoming movies of The Justice League/@comment-28983864-20160415102055/@comment-1038387-20160415103455

Actually, Flash is DC.

As for the OP's concern: The TV verse and the movie verse are not the same, and were never meant to be the same. DC didn't replace Grant Gustin. The two Flashes exist in different universes. Different Multiverses, even.

Grant will continue to be the Flash for at least another season, and who knows how long after that. He was never in view to be in the movies.