I would expect basically a 9800XT, but with higher clocks and better PS2.0/VS2.0 performance. So maybe 10% faster than a 9800XT, depending on the app. Or, in other terms, yes, around half of an X800XT. At $299, this is a 'midrange' card in terms of pricing, at least for the next generation (a little scary, huh?).
I wouldn't be surprised to see a 4-pipe variant come out for the low end -- or ATI might even just keep making 9600XTs for a while. Saves on the development costs, and then they can put out a new 'low-end' card when they go to PCI-E.