TLDR: Bitcoin will reach is cap of 21 Mil. Miners will have to resort to transaction fees as incentive for mining. Bitcoin community will ultimately agree to raise Bitcoin cap and inflation will become normalized for Bitcoin. This will solve high transaction fee issue but will lead to a slippery slope.
You can't even predict what will happen 100 days from now, how can you even begin to predict more than a 100 years from now?
In any case I always like to refer people to the history which will continue at least for the foreseeable future. Back when miners were earning 50 bitcoins per block that were barely $1 but today they are earning a small amount of 6.25 bitcoins per block but that is worth more than $250,000. I'd say miners are receiving way more higher incentive than they need to start looking for fees.
Bottom line is that we can not predict something that is too far away in the future.
I came across Steemit, which is in the STEEM blockchain. Steemit is interesting because they reward users for posting and curating content that receive a lot of support (upvotes, comments, etc…). They are able to pay the users the participate by inflating their own token.
That's not on steem blockchain, that is all happening on a 100% centralized website that could pay users in a semi-centralized token on steem blockchain.