The top-tier card MIGHT be but it's not that simple. Compute Units, like shaders, don't scale linearly unless you can keep them all working all the time. It's possible that the RX 6900 XT(X) is twice as fast as the RX 5700 XT but that can't be confirmed just by looking at the number of CUs. Things like IPC, clock speed, cache size, cache latency, VRAM speed and VRAM bandwidth also have to be taken into account.Surely it'll be twice as fast as a 5700XT with these shader counts.
It's impossible to know for sure with the changes AMD will have made for RDNA2, and the sustainable boost clocks. However it's gotta be a safe bet.
That would put it well over the top of a 2080Ti but probably short of a 3080.
Even then, you still won't really know because when actually using the card, the efficiency of the drivers and the optimization of the actual game in question also come into play. That's why, despite all of the leaked
Until then, all we can do is guess. We might be close or we might be way off. Remember, on paper, the Radeon VII should be faster than the RTX 2080 Super but it's not because these things aren't so cut-and-dry. There are far more variables than constants and that's kinda what makes it exciting.