The next train set might actually come from the Toy Story line - the Western Train Chase. While clearly aimed at a younger audience, the set includes some interesting, useful parts.
We've known about this one for a while, but better pictures just recently surfaced on Brickset.
Note the one-piece cowcatcher, green 2x3 windows, log elements, 2x4x2/3 curved slopes in red (on the locomotive cab) and red train wheels in small and large sizes. (I believe the earlier pictures showed the wheels as being black.) Also, you get Dino - who we haven't seen in a set up to this point.
The especially keen viewer will note that in the above image, the caboose is following the locomotive rather than bringing up the rear.
Adult train builders may find this set a bit pedestrian, but consider: sets like this help to create the next generation of LEGO train fans and get kids excited about trains. With a sizeable gap between Duplo trains and LEGO City ones (not to mention the PF lineup), this set may be just the thing to bridge the gap.