What happens if bitcoin mining stops or becomes too expensive? Is that within the realm of possibility? Are there mitigating factors, probably the adoption of renewable energy?

Whether it's renewable energy or non-renewable energy, you will lose energy. If you consume energy and lose money while mining, it's natural not to mine. If mining stops, Bitcoin will dominate the market with the same amount of supply as it has. However, the current price of Bitcoin will not remain the same in the future, and if this price remains, mining companies will go bankrupt and stop mining. If the big mining companies stop mining Bitcoin, then there will definitely be a severe impact on the market.