After pondering this a bit more, I think that agreeing on some economical aspects of the protocol in the future is exactly what Bitcoin is for.
Yes.
https://en.bitcoin.it/wiki/Prohibited_changes
Require unanimous consent
These changes require the consent of every bitcoin-holder:
Increasing the total number of issued bitcoins beyond 21 million. Precision may be increased, but proportions must be unchanged.
Any rule that adds required, explicit centralization. For example, a change requiring that all blocks be signed by some central organization.
Demurrage (deletion or reassignment of coins judged to be "lost" or "unused"). This is highly controversial in the context of currency units; on the other hand it is absolutely essential for namespace entries like [Namecoin] (which implements Demurrage for namespace entries but not for currency units).\
I would also add 2 more aspects that should be classified under "Require unanimous consent":
1) Anything that harms fungibility such as reversible blockchain transactions or blacklisting.
2) Explicitly weakening the inherent pseudo-anonymity of bitcoin where individuals aren't empowered to choose their degree of transparency vs privacy
Require miner consensus Changing the bitcoin distribution algorithm such that the subsidy at any given time period is decreased without miner consensus and 3 years notice, or increased beyond improved precision of halving (lossy beginning with block 1,890,000).
Disputed Adding alternatives to Proof of Work such as Proof of Stake. This could change core bitcoin too much, but with widespread agreement of some sort might be possible.
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This hardfork to adjust block size is categorically in the 2nd section requiring miner and full node agreement with a slow and careful roll-out and trying to reach consensus by the community first and allowing them to address their concerns.
I think the categorization of protocol changes above would need to be re-evaluated at some point. I believe that PoW scheme is more fundamental to Bitcoin, than any other aspect of the system, for those additional degrees-of-freedom it provides for the competition (this has been discussed a lot recently).
However, the block size limit, the tx fees structure and even the infamous 21m limit is where it gets interesting. These things are actually inter-related and not completely orthogonal. If it happens that fees are not able to provide enough incentives in the future to keep the network secure, then introduction of permanent limited inflation would be one of the options on the table, no matter how unpopular it might sound today.
Some balance would need to be found between the costs of transactions for active economic participants and Bitcoin's ability to maintain value throughout time for savers. The presence of other similar systems in the environment would not allow one system to swing too much in either direction. If transactions are too costly, another system with higher block subsidy will provide less friction for the commerce, if inflation is too high then another system will gain more traction as a store of value.
This will be very interesting to see unfolding and I would expect a lot more debates in the future for finding the right balance for Bitcoin. People will learn economics by working it out on a live system with their efforts rewarded in terms of growing adoption and increased monetary value. There will be winners, there will be losers, but everyone is given a chance to participate and make their choices, that's invaluable.