Honestly?

I think it will become irrelevant, yes. 2-3-10 years, who knows. GPUs are not really that efficient. They are just easy to get their hands on. Unless you have very, very low ct/kW rate, it already doesn't really make much sense anymore.

Then again, who knows. ETH's shift to POS will be interesting to say the least. You'll need a minimum of 32 ETH to stake afaik. I have no clue how much that will yield to.