There seems to be something happening imminently at GDC, according to the LucasArts
twitter feed. They suggest you follow their updates. Exciting times!
Edit: According to some of the tweets, SoMI:SE is coming to Mac and PS3. One of the fans LucasArts invited said it's coming to the Telltale site. Which is awesome. This is apparently announcement one.
Announcement two? MI2:SE.