Buried in the massive infodump of today's Warner Bros DC Movies announcement is the identity of the new Flash, and it ain't Grant Gustin, who is already playing The Flash on TV. It's Ezra Miller, a really great actor who has been sensational in We Need to Talk About Kevin and The Perks of Being A Wallflower. He'll be in Justice League and then getting his own solo movie in 2018.
I have to admit I don't get the DC model. It seems very likely that The Flash TV show - which is good, based on the pilot - will still be on the air when Justice League comes out, and probably by the time The Flash movie comes out. I think it's kind of odd to have two different Flashes running around, especially because Kevin Tsujihara says that the show will be helpful in getting audiences into the character.
As for Miller himself - he's a good actor, but god is he willowy. The kid's a beanpole. I can't imagine him having the strength to run to the end of the block, let alone at Mach 1. But we should have a chance to judge very soon - my sources tell me that The Flash is in Batman v Superman: Dawn of Justice*, as is the rest of the Justice League. They're all together at the end of the movie, ready to face the larger threat that has manipulated Lex Luthor and maybe even Bruce Wayne.
* the actual title. This would have been a good day to change it.