They're horrible buys, especially the GRE - a gimped 7900 series because of defective dies. Wow, I just can't even...RDNA4 won't have a top end card, highest will be Navi 48. Rumored to be around 7900 XT performance.
More than likely they are going to package this in a "8800 XT" build for around 400-500$
Thus if you need a GPU now, 7900 GRE / XT / XTX are not bad buys. They will be around for awhile and some will have better performance than the top RDNA 4 card at least in raster.
If you don't need a card right now, and/or want to hold out for the latest and greatest, at least you know what's coming.
Personally, I'm finding the 7900 XTX performance being... less than I want. I mean it was a fine upgrade over my 5700 XT, but I'm not keen on skipping another generation. I'm not sure I want to wait another 3ish years for a high end card so I'll have to see what the RTX 5090 offers and potentially look into that for a future upgrade.