I can see it making sense to remove curation rewards once SMT's become the backbone of how rewards are distributed. Steem, IMO, is not a rewards currency (right now it serves that purpose, but SMT scales much better) - however, it is a distribution currency. DPOS being a vote based system requires great distribution to succeed in the long term. 
While removing curation rewards down the road, makes sense from an investor POV, not forcing me to curate in order to get my rightful claim to the inflation, I wonder if we do remove curation would we remove the upvote from the base layer altogether and just direct that to passive interest earned for powering up steem? 
And what immediately comes to mind by removing curation is the need for a decentralized resource leasing market, because people need steem to transact on the blockchain, businesses will need to allocate resource credits to new users who don't have access to Steem. - I envision most Steem will be locked up, not being circulated (esp if we remove curation, distribution will decrease dramatically) but rather used to power apps. It may be hard to find steem, or at least the price to entry may be too high for someone just looking to join a steem powered site and not care about paying for the rights to vote on witnesses, ETC.