Obviously the numbers in the LLM case are much less certain given that I'm guessing based on qualitative improvement and looking at some open source models,

Sorry,I don't follow why they're less certain? 

based on some first principles reasoning and my understanding of how returns diminished in the semi-conductor case

I'd be interested to hear more about this. The semi conductor case is hard as we don't know how far we are from limits, but if we use Landauer's limit then I'd guess you're right. There's also uncertainty about how much alg progress we will and have met