We've only just seen the announcement of the NVIDIA GeForce GTX Titan Z, and the proper release of the AMD Radeon R9 295X2 dual-GPU card, but now we're hearing about AMD's next-generation single GPU, the Radeon R9 390X.
If the rumors are true, the Radeon R9 390X has a codename of Bermuda, with a family name of Pirate Islands. The Pirate Islands-based GPUs will be baked onto AMD's 20nm process, succeeding the Volcanic Island GPUs we all know and love today. The Radeon R9 390X would be quite the beast, featuring 4224 Stream Processors, 264 Texture Units (TUs), 96 ROPS, a Core Clock of around 1GHz, Memory Clocks hitting 7GHz or so, and a super-wide 512-bit memory bus.
Comparing this against the Radeon R9 290X which is already powerful, the R9 390X will trump it, easily. The R9 290X for comparison sake had 2816 SPs, 176 TUs, 64 ROPS, and similar core and memory clocks depending on the card (third-party cards can overclock very high).