A forum member on Chinese website has leaked a 3D Mark Vantage Extreme benchmark, alongwith a GPU-Z screenshot, alleged to be from a next-gen ATI Radeon HD 6870.
20-30% faster than the 5870 is in line with what was being talked about for a long time, so this could be real enough. I'm interested to see what the power draw is like, hopefully we wont have to wait too long to find out.