The upcomming RX9000 series uses almost double the power usage regarding their counterparts so i do not see a reason to wait for those cards unless you need extra heating during winter.
And as far as i can tell from reviewers, the uplift is not worth the price at all.
So get the RX6700 XT unless you need the AV1 encoding embedded in the RX7600 XT.
But even better, get the ARC B580 if you are a content creator and/or streamer.