Well, after that trailer, it definitely looks like a step-up from Shrek the Third. Still, I can't shake the feeling that this "what-if" storyline seems highly unnecessary, but if they felt this would make a better ending than the last movie, then more power to them.
Gotta admit, the visuals in this film look really good. The environments look really detailed, even for the sections that look like a total wasteland. That opening scene in the carriage alone is very nice to look at.
So who's the dwarf guy supposed to be anyway?