SMT's will have an internal market which Steem would be the main currency it trades with and the utility from sp allows you to do everything on the chain.
This wouldn't centralize anything, this would just switch how the mining is done. Instead of focusing on content for the main coin it would turn more into something that is used. Steemit can have its own smt just like anyone else that could be traded for other cryptos and Steem.
RE: Part 3 of Our Plan to Onboard the Masses: Smart Media Tokens