That's not the case, see
from
http://www.techpowerup.com/53358/GeForce_9_Series_Roadmap_Updated.html. Higher number doesn't mean the better chip, it's the 9600 that uses the G94, the 9500 uses the G96, the rest are all the G92 used within the 8x00 series cards released last fall/winter
Trog above pretty much nailed what happened.. the G9x chip was Nvidia's next gen chip. ATI had two good cards coming out within the 38x0s. As a pre-emptive strike Nvidia rushed out some versions of the G92 cards (remember how stock supply was such a problem for them? That was probably b/c of the rush job) as 8x00 series cards. The GT and GTS should have been 9800 cards, but for one reason or another (most likely they didn't want to introduce them as the new gen when they may not have been completely ready and the other variants were also not ready yet) they were solds as 8800s. It's less that Nv is trying to rebrand an old card as much as they improperly branded a new card. But one way or another though don't expect too much of a gain on any of the 9x00 series cards over what we saw of G92 chips among the 8x00 series b/c the changes will mostly be tweaks.
While there's some truth to what you're saying that's probably not completely fair... first of all if you remember ATI did originally plan on releasing those cards as 2x00 series cards. In the end given all the changes (die shrink, consequently lowering power consumption, consequently fixing the considerable heat and noise issues with the original 2k series cards, and other changes that let them sell the cards considerably cheaper), and the fact that those changes represented a lot of the major problems with the 2k series cards it's hard to blame them for the name change (if I remember correctly they did state that they specifically wanted to distance the new cards from the 2k s).