It could be any GPU, I don't buy that this is big navi. I could see big navi maxing at 16GB, but I think the lowerer model would also come with 16GB option.
That said I don't see AMD competing with RTX 3090, I think they are going to have a card that is a bit slower than the RTX 3080, probably about 15% slower, but costs $100 less, and then have a RTX 3070 competitor that is about 10% faster at $500.
So a RX 6900 at $600 with 15% less performance than RTX 3080
RX 6800 at $500 with 10% more performance than RTX 3070
RX 6700 at $400 that is about 20% faster than RX 5700XT
RX 6600 at $300 at about 20% faster than RX 5700
RX 5700xt is likely to be discontinued
RX 5700 likely to be sold at $250 price
RX 5600xt at $200
RX 5600 at $170
RX 5500xt at $140