RX 470 and 460 specs showed up on Techpowerup GPU database.
RX 470 has 3.7 TFLOPs and 100W TDP, around 380X performance.
http://www.techpowerup.com/gpudb/2861/radeon-rx-470
RX 460 has 2.5 TFLOPs and 75W TDP, around same performance as 370X.
http://www.techpowerup.com/gpudb/2849/radeon-rx-460
Polaris look to be very underwhelming. Shocked AMD had learnt absolutely nothing from Radeon 285 Tonga massive failure at all. Nobody interested in energy efficiency 285 that had same performance as 280X but with few new features, AMD fans wanted more performance.
I think AMD is very nervous about Polaris now, they don't know if it will be successful or another failure like Tonga.