I think a 10x in purchasing power will go a long way to tempering blockspace demand. It will become so tempered that people will stress about mining incentives again.
We're currently very early still with less than 1% of the people in world having UTxOs to move. With time I think the timechain becomes used primarily for maintaining liquidity in L2 networks & settling very large trades. It simply becomes too expensive for most people to be able to or to justify transacting on.
We'll still see spikes in demand but we just don't know what the Tx fee market will settle upon.
In the next 10 years I suspect fees will drop on average (in sats/vB) compared to the prior 10. I think that at some point we hit a bottom, where only the most necessary of transactions are hitting the timechain. At that point, fees start steadily increasing (miner death spiral avoided) again.
My point is that there's a lot of complexity & uncertainty around the future of the timechain fee market.