SMTs and Communities are being developed in parallel and are independent of one another. Communities is non-consensus which means that we can begin releasing features as we develop them. That means you should start seeing Communities features implemented in some front ends well before SMTs are released. With respect to SMTs there are two important milestones, when we release the Testnet, and the hardfork date. We have much more control over when we release the testnet which is basically a way for developer to "play" with SMTs before they are released. However, in order for SMTs to be added to the Steem blockchain, a hardfork is required and that is a much more complicated process which requires that we coordinate with the Witnesses and Exchanges to ensure there is a smooth transition between forks.