There hasn't been a release date yet more than "first half of 2017" which probably means late spring or later (would expect a similar launch date as the rx480)
Since nobody has tested these chips yet as they aren't released no-one can say for sure.
But given that the Rx480 is already at the level of a 1060 and that unlike CPUs GPUs advance quite a bit with every generation, I assume the weaker rx500 cards will compete with a 1070 while the top line will be a good deal faster than the 1080. Everything else wouldn't make much sense to release.