I think it's about the audience it's directed towards. The trailer looks like it could be geared to more of a teenager audience. Just like quite a few popular animes like Naruto and Bleach, which are directed more to the teenager audience. If they made pokemon more serious and explosive and intense like in this trailer, then that would make one wicked anime.
The problem I have with the current anime is how obvious and annoying everybody sounds when they open their mouths. Like when Iris is saying, "A dragon type pokemon like Axew is weak to an ice type pokemon like Vanilluxe!" is just so annoying to hear when you've been playing the game for years.
There's another thing that annoys me, and that's the plot. Ash just goes around defeating three team rocket thugs and earning badges. Every. Single. Season. And it's the same ten year old character over and over again! Give us some new material. Maybe show a sub arc with Barry in it at the Sinnoh battle frontier and earning all the symbols so he can face his dad and prove to him how tough he is. Show us the new BW 2 characters and give us a new plot with team plasma in a frosty region in unova. So it isn't entirely centered around earning badges, but also about stopping team plasma.
And please, let Ash hit puberty, let the main character's pokemon evolve to it's final stage (I don't care if it's Ash or someone else, just let them evolve for crying out loud), and please, please don't bring Dawn back. I hated her with a passion.