It actually sounds like Keras as we know it will continue to exist and support both Theano and TF.

Theano support will continue for as long as Keras exists. This integration changes nothing for existing Keras users, only for TF users. - https://twitter.com/fchollet/status/821090410659344384

Rather than a "new" Keras it sounds (I could be wrong) as if the Keras API will be included now with TF as an alternative way of interacting with TF (as it has been for some time) and simple bundled with TF.