Seems like people are going to take a large haircut on whatever they deposited and then maybe get back some incremental cash over time.
2) the hardware is going to become obsolete well b4fore 7 years (although I wonder how the semiconductor shortage is holding back custom mining hardware design and manufacturing? Maybe in 2029 people will still be using today's hardware? I seriously doubt that.)
3) I'm reasonably sure arbitrage pushes the cost of mining asymptotically close to the price of electricity to run it, so the margins are almost all whatever temporary, fraudulent, or criminal steps you can take to reduce your cost (or outright steal) the electricity.
https://www.bloomberg.com/news/articles/2022-03-07/electric-...
My rates are 11-13 cents per kWh, the same as they’ve been for years. Our power is mostly hydro, with smaller amounts coming from nuclear and wind.
So no, that pithy question isn't particularly useful.
The miners will mine as long as it is profitable since they need to recoup the costs of specialized hardware somehow.