What we can extrapolate is that the 7900XTX would have around 50-60% more performance than the 6900XT in pure rasterization games, so without RT, and all that FSR/DLSS bullshit. So look at some benchmark on the 6900XT and take a guess, while its RT performance might not be up to par with the 4090, since its about a generation late in comparison, its still up to 50% greater than before, which probably put it in the ballpark of the 3090/3090ti RT performance, which is still far below that of the 4090.
Then take into account the price, it would probably be far superior than the 4080, in most games barring RT performance, then it's also cheaper, $999 vs $1199, so it definitely a better choice IMO. The 7900XTX might not be targeting the 4090 especially at it's price point, instead the 4080.