Although on the flipside, let's pretend it's 2017's and you are Nvidia selling GPU's for Bitcoin - maybe demand will dry up at some point? Do you stop scaling production as this might be the max of the market, or do you follow the market and increase production?

It's always easier to see the right move in hindsight!

Nvidia doesn't own fabs though, TSMC does. By 2017, ASICs for Bitcoin were well underway. Ethereum hadn't switched to PoS, and wouldn't until 2022. For that specific question, the answer is yes, because the GTX 1080 Ti is/was a monster card, and the crypto miners have a somewhat predictable demand for them, so there's some modeling you can do based on demand for the 2016 generation of cards. The question is ofc, if you're Nvidia, what are you optimizing for? Let's say, without foresight that Ethereum would move to PoS in 2022 and that AI would replace that demand, how many 1090 Ti cards do you make, how many 1070s, how many mobile 1080s, how many Titans? In order to answer that, someone at Nvidia would have to have, for better or worse, really had to have gotten into cryptocurrency in order to understand that market. Because you, as Nvidia, know how much better the 1080 will be for mining Ethereum, certain predictions can be made on demand.

Question is, without hindsight, 2022 rolls around, Ethereum moves to PoS, do you sell NVDA?

Its a lot easier to commit to spending billions of dollars in a hypothetical then reality.