Any feedback process has a hard threshold for instability. The PA system doesn't howl until the microphone is close enough to the loudspeaker. The atomic bomb doesn't explode until the fissile material reaches critical mass. If you don't know where the threshold is you can't extrapolate.

Compute is a limiting factor now, but there have already been huge improvements in compute efficiency, e.g. mixture of experts. It seems extraordinarily unlikely that there are no more to be found. And compute capacity continues to increase too.