I don't think everyone should be so negative.
When I heard Jackson was doing LOTR I couldn't believe it! The Jackass who did Bad Taste! Come on, it will suck! And look what he delivered.
It will only fail if the studio does not find someone who loves the source material, as Jackson did/does for LOTR.
The studio took a huge risk in Jackson (as did the Tolkien estate) and there are plenty of good film makers out there.
I vote for Guillermo del Toro (Pan's Labyrinth), Sturla Gunnarsson (Beowulf & Grendel) or John McTiernan (13th Warrior)... even better would be the brilliant Josh Whedon!
It would be a shame if Sir Ian and Serkis turned down their roles but not the end of the world.
Before LOTR, who the hell knew who Jackson or WETA were? There must be directors and SFX units out there who deserve such a chance with the Hobbit and frankly, the thought of the Troll capture scene, a whole cast of Dwarves and Smaug... makes my entertainbuds (new word coined for this thread (C) ) drooooool.
Shame on you.