Just thought I'd post this for a lark. A fake 5870/50 "review" I made
I used these assumptions, that 5870 would be 1.6 times as fast as 4870 per the rumor, and then that 5850 would be 83% as fast as 5870 (based on the fact 4850 was clocked 83% of 4870). And I randomly used the benchmarks from this
review (I used the stock clocked cards benchmarks only).
Also it's not particularly readable, as I've never made a graph before, and just used some online graph maker website.
If you assume the 399/299 price points, (and pretend these benches resemble reality) 5850 is probably the more interesting card. It's an easy sell next to GTX285, as it's faster, cheaper, and DX11. However it does get some competition from the $200 4890. The main drawback of the 4890 would be that it isn't DX11, and I wonder how many people will trade that off. Of course if it turned out 5870 was 299, then all bets would be off.
Edit, I may be lowballing 5850 too. If you assume it's 1600 shaders, and clocked conservatively at 600 mhz, then it has 41% more shader power than 4890. Yet my benchmarks it only averages ~22% faster (Of course it could be texture limited etc). So there may be upside to both these cards over these assumptions if anything I'd suspect.