Update:
We have some more details on the Polaris GPU's.
The R9-480 is looking like a pretty great card. It MAY be up to 20% faster than an R9-390 and cost as little as $200MSRP. That seems a little too good to be true, but that's the info we have as of yesterday.
Still, it's looking like AMD will have a great value lineup in the $150USD to $300USD price range.