The Merge took years of planning and testing to deploy, and Ethereum's network is not as old as Bitcoin's.

Even if Bitcoin were to migrate to PoS, it would not feasibly occur in the next 5-6 years.

By then, we could have just chosen to continue addressing the issue of energy sources used in BTC mining, and placed greater emphasis on minimising e-waste from discarded mining equipment.

Long story short: Bitcoin will not switch to PoS.