Well, we do
, in fact, get to see an image of Smaug in the trailers: On the map.
But there's no real reason to show the fully-rendered version until the trailer to The Desolation of Smaug
. An Unexpected Journey
will be served by the pent-up demand for a Hobbit
film and the trailers featuring Gollum. And IIRC, there weren't any trailers attached to the ends of FOTR or TTT. I'm guessing our first look at Smaug may be with the teaser to Desolation
, and/or, perhaps, Comic Con 2013.