Early benchmarks show the 480 trading blows with the 5870, not just the 470. Obviously in games that favor the Fermi architecture, the 470 could probably be as fast as the 5870. The 480 would be faster in those cases. In games that favor Evergreen, the 5870 could be as fast as the 480 and so the 470 would be a decent amount slower. It's not unlikely.Well according to the "benchmarks" that are out already, the 470 exchanges blows with the 5870.
So if the 480 does as well, as your theory states, then that means the 470 and 480 could possible go back and forth as well.
I'm going to say that isnt likely.