There are benchmarks already of pre production samples. The results might change a bit after release but still give a direction.
From those benchmarks I can tell that the "12900K" (the equivalent of the 12th gen top cpu model) may have an IPC value as large as 25-30% better than that of the 11900K and that is really good. If this holds it will be 60% faster than my 9900K.
It might be possible to OC it to 5.3 GHz on all 8 "big" cores simulaneously. Its multicore performance will probably be better than that of the 5950X (honestly, it must be, anyway).
And, again it will probably be a very unefficient CPU.