According to benchmark figures listed on the GFXBench database, the upcoming Radeon R9 480 graphics card could deliver performance very similar to the Radeon R9 390X.
We cannot be entirely sure though, as we only get to see the OpenGL benchmarks on GFXBench. Still, it is definitely a positive sign and raises out expectations from the card. It should be noted that the Radeon R9 480 will be manufactured on a 14nm process and is likely to have a power-draw half lower than the Radeon R9 390X and could be priced at around the $200 mark.
The Radeon R9 490 on the other hand, is expected to be equally impressive, offering performance close to what the current $600 GPUs offer at almost half the price.