There are a lot of them, some in this thread. The early reports seemed to indicate a die shrink. The later ones now indicate only the low end OEM garbage will be a die shrink rebadge. I agree with you (and had stated it in the past) IF the 7850 is a VLIW4 on 28nm it will be a monster card. Sadly that doesn't seem to be the case.
If that's the case, then I'm really disappointed. I'm quite reluctant to jump into FPGA's anytime in the near future, so I was hoping I could get some power efficient cards in the meantime. Grrr.
I have to break it to you but those number are pure crap for a 5970. Not just against what I have gotten but against what lots of other people have gotten. The limit on each card varies but my slowest card is running 820Mhz/160Mhz. 3x5970 in open air rig pulls 870W at the wall (measured over 3 days using kill-a-watt). Backing out 100W for the MB, power supply inefficiency, CPU, RAM, etc that puts each card @ roughly 250W a piece. That is w/ cgminer 2.1.0 running on Linux w/ 11.6 drivers & 2.4 SDK.
If you aren't getting AT LEAST 700MH/s you are doing something horribly wrong. Note: 700MH/s isn't "good" it is just barely acceptable.
My math was bad in my previous post. 340x 2 = 680, not 640. That's what happens when you've been up all night without sleep
Most of my 5970's I have been running at 800Mhz, but stability has sucked (suckage = a stalled miner once in three days), so recently I've dropped it down to 750-ish. I'm on pretty much the same setup as you. Ubuntu 11.04 x64 with 11.6/2.4 drivers/SDK, though I use phoenix directly with my own scripts. I'm sure I could get more out of the 5970s, but I simply don't have time for that.