My line of reasoning goes like this:


How does the network sustain itself?

• Block subsidy
• Transaction fees

Which one is definitely going to stop sustaining the network?

• Block subsidy

Therefore, which one is the main compensation for the network's survival?

• Transaction fees

Does this mean that transaction fees need to be expensive? Two answers:

• Yes, because Bitcoin has scarce block space. Therefore, with ~3000 regular transactions per block, to cover 3 BTC (which is currently the block reward), each one has to pay 0.01 BTC, or 4000 sat/vb, for a typical, 250-byte transaction. Hopefully, we will need less than 3 BTC per block.
• No, we can arbitrarily increase the block size, so that we have more on-chain transactions, each one paying much less. This comes with several tradeoffs, of course, like the risk of lacking competition for block space, which would without doubt result in a network dying out of starvation.
• No, and as a response to the lack of competition, we can violate the hard cap, and add tail emission.

The roadmap of Bitcoin, in my view, is set in stone in 2017, with small blocks and backwards-compatibility as the status quo, and it is the first one. You can find altcoins that have picked #2 or #3.