We do not know how large the Hydro Copper block is yet nor do we know if any other brands will make one for the FTW3. EKWB is a decent bet that they might though. If we compare the aircooled versions of FTW3 though, I think the 3090 is actually slightly smaller.

Yes they are. They are 300 x 136.75 x 55.55(2.75 slot). Literally have them memorized at this point , haha. In comparison the 2080 Ti FTW3 was 301.925 x 139.3 and 2.75 slot.