Over time as the number of transactions increases as bitcoin become more widely adopted the amount of TX fees per block will increase, while the TX fee per transaction will likely stay the same or decline.
This straight from the Bitcoin wiki
But I disagree with the core developers on this one, Satoshi has not been incorrect yet and their calculations are likely right on the money we are preparing for something that is going to be proven incorrect in the future in my opinion.
A fork or a sidechain reward will become increasingly likely and implemented as halvings occur in the future and the rewards basket will increase without mixing up the core transaction protocol, a bunch of merge mines like with Namecoin could make that difference basically miners will still be able to acquire subsidies in one form or another as more developments occur.
It's fine to discuss it but I disagree on the need to implement it until a few years down the line.
http://bitcoin.stackexchange.com/questions/273/how-does-merged-mining-workBased on the abstract since I can't read the full PDF
The paper argues for a lack of supply and scarcity basic economic tenets and arguments but does not include the idea of unconventional and new supplies being acquired in the terms of new sidechains and merge mined coins.
Pretty much its like comparing a theory based on Hubbert's Peak versus one that is based on a Mckelvey box completely different approaches to the same conventional question with one being superior in accuracy to the other.
http://sdiwc.net/digital-library/near-zero-bitcoin-transaction-fees-cannot-last-forever.htmlWe will see though but I would be against this implementation for now although the safeguards to make it in case seem fine with me.
(Background information Hubbert in the 1970s predicted Oil Supplies in the US would fall rapidly and prices would increase he was spot on and it became canon in the oil industry for a while)
But at the same time he based it on traditional extraction methods and as new ways to acquire oil became possible the supplies increased because he underestimated the unconventional supplies and emergence of new technologies that allowed for Deep Sea Drilling or Fracking.
My argumentation for a Mckelvey box is that these new supplies when applied to cryto are sidechains and merge mined coins alongside the Bitcoin protocol that will incentivize the miners and secure new supplies in a sense.
Kind of like using Oil to make byproducts such as plastics etc not a zero-sum game but a multi-sum one with various rewards.
http://en.wikipedia.org/wiki/Hubbert_peak_theoryhttp://en.wikipedia.org/wiki/Mineral_resource_classificationSo rather than being unsustainable I would argue that is far from proven and is nothing more than a theory at this point in time, but we will see in the future which scenario will ring most true.