There is NO prices confirmed from nVidia yet, so lets wait and see.
Here are my guestimates :
GTX470 - $449
This is the best prices for nVidia to not flame price war and still sell good, but it also is good for ATI as they can continue selling their cards on current prices. After all the loosers will be us the consumers
My thoughts on the situation is that if nVidia somehow manages to outperform 5870 with 20-25% consistenly then they are in some kind of safe zone as even the 5890 (only rumor) wont be over 1Ghz mark which is about 20% theoretical performance and more likely 10% real performance improvement.
This will mean that Fermi will stay on top which is what nVidia would want desperately. If however Fermi is only 10-15% faster then its in this unstable spot vulnerable for counter attack.
I personally would like it to be 20% faster which will bring us to the old 280GTX 4870 , 4890/285GTX price wars - nVidia staying on top but ATI dropping prices aggresively.
If Ati outperforms nVidia with 5890 say bye bye to cheap Video cards as nVidia wont drop the prices as they cant afford it and ATI wont have to so they will exploit the situation
looking at this it seems 470GTX is about same distance from 480GTX as 5850 from 5870
going from that I would calculate that 448 to 512 sps is almost same diff as 1440 to 1600, thus to get same performance 480 GTX would have to be about :
725 MHz core and ~1500 shaders - Highly impossible by my opinion.
More likely I would put it to 675 core and about 1400 shaders which would not mean in such performance and can quite fall into 105%-110% over 5870 (average)
I am sure there will be games where fermi stomps 5870 but also there will be games where it will loose to it (proof to that is if Fermi beats 5870 everywhere and in every ocasion we would have seen trilions of benchmarks showing off from nVidia)
The secrecy means they want to play very carefully and adjust the information flow and comparrisons as much as they can to present their baby in the best possible shape