That's not very useful. That curve might be a combination of a few different bottlenecks, l1 cache misses, scheduling bubbles, efficient scheduling of instructions within a certain window, l2 cache misses, cache contention in L1 or L2, AMX utilization, memory utilization (latency or bandwidth limited), MMU contention/page misses, etc. etc. etc.

The percentage of all those can change as you change the number of cores, and the different levels of the memory hierarchy get different levels of contention, latency limits, or bandwidth limits. So in an ideal world you can draw a graph and extrapolate, but in the real world you might do significant better or worse. There are cases (admittedly rather rare) where performance increases by more than linear in relation to cores.