Slashfilm (or /film, or whatever) is reporting that Executive Producer Ronald D Moore explained that due to a "scheduling conflict" Smith is no longer attached to direct an episode.
When asked if they will have to issue a statement to the media, Moore said “No, they probably won’t. Something like that only registers on message boards.”In other words, they would rather that Smith had not bragged about helming an episode in the first place and they probably pulled the plug on his dream as a punishment for blabbing about it online.
So far there is no news about it on NewsAskew or Kevin's own blog (where he would rather talk about "tugging one out" to induce sleep over any real film news). But we're guessing this will hit big with the fanboys soon enough.