You have to understand what the new engine is showcasing here, the U4 Engine is all about particles.
If a machine, PC or console were to attempt to render every little bit of ash, snow, and ember in the demo, you'd experience some of the worst frame drops ever to plague a modern GPU.
That they can pull off that much particle processing in that demo AND for it to look that good, after only being thrown together inside of three months is quite a feat. They executed a Blizzard-esque cutscene - only that it wasn't a cut scene - that was all rendered/processed in real-time bears some applause. There's also another tech demo out the for the engine called "Samaritan", I believe.
Also, this isn't a game trailer - for those citing a lack of gameplay. It's just a display of horsepower, if you will.
Lastly, and on a somewhat related note, check out a site called "Deadend Thrills", and have a gander at how amazing modern games can look, once all the 'crap' is stripped away.