The RX7900XT is about 30% faster than an RX7800XT,so even if the uarch was the same it would get close to an RX7900XT looking at the specifications.
The bigger issue is pricing IMHO. I just hope AMD don't try to price it relative to scalper pricing. I remember that happened during the Pandemic and I found an RTX3060TI FE for around £100 cheaper than an RX6700XT. I wanted an RX6700XT!
People have to understand the Pandemic is over and all we are having is artificial scarcity to push prices upwards. Best for people to not bother buying from both companies if they try more price fixing IMHO!