What are the long-term consequences of the decline in Bitcoin block subsidies on network security? Also, what are the mitigation strategies?

Bitcoin’s security model is currently supported primarily by block subsidies, encouraging miners to donate to hash power and protect their networks. However, block subsidies are halved about every four years, and asymptotically approaching zero over time.

This has led to concerns that in the long run, transaction fees alone may not be enough to provide the same level of security, potentially leading to lower hashrates and increased vulnerability to attacks such as Deep Reorgs and 51% attacks.

I am interested in both theoretical and practical implications of this transition. in particular:

What are the expected outcomes of the decline in block subsidies on minor behavior and overall network security?

Are there any past rate market trends that suggest whether rate-based security is viable?

What mitigation strategies are being proposed or discussed, including tail emissions, protocol changes, and layer 2 mechanisms that can support L1 security?

I’m asking from both the engineering and economics perspective. If possible, we appreciate any references to existing research, suggestions, or data-driven analyses.