AMD is not competing with 1080, so they are not in a rush to release polaris.
the question is, do they have the performance to compete with 1070, if they do, they will release polaris before june10 at least on paper with full disclosed infos.
if by june 10 we still dont have more info about polaris 10, then performance is too low to be competing with 1070.
Considering the 1070 is such a cut down version of the 1080, then I believe Polaris will be able to beat it.
Though all NVIDIA have to do is crank up the gameworks effects to destroy any real advantage AMD may have, making the 1070 the safe bet. (IMO).