True, nintendo does not have a history of "bullshot"-ing videos and screens, but Ubisoft certainly does. Given the hardware estimates of the Wii, the graphics of the other trailers and reported hands-on accounts, it can be safely concluded that while the visuals are definately on par with or better than xbox and GC games, they certainly aren't cutting edge.
Yes, they could very well be in-game shots. But I'm going to assume that they aren't for the time being, until I see high quality direct feed footage or screens.
EDIT:
According to the hands-on reports today, the game is lacking visually. In particular, the models and faces are quite blocky. My guess is that the screens and trailer are the game running on a PC, and are hopefully of "target" quality. Ubisoft apparently did not recieve near final dev kits until the end of March, and I'd assume/hope that the visuals are still being tweaked and optimized for the crossover from PC to final Wii hardware. So far, the physics and AI look like they are well in place, and one would hope that Ubisoft spends the next few months refining the control (reports say it is too sensitive) as well as getting the actual visuals up to par with the trailer.