Theory on future events...
I'm not a Star wars freak but here goes. You experts tell me what you think.
I think some how some way Padme falls out of love with Anakin or maybe even thinks she even thinks Anakin is dead.
She's pregnant with the twins and maybe marries again into the Organa family of alderan. She later dies out of sadness...maybe cuz of what anakin becomes or even if she thinks anakin is dead.
As a result, with Padme taken away...his "fear" propells him into the dark side. we already sees his anger at losing his mom. Now losing Padme drives him over the edge.
ALso, in the trailers...you see him referring to Palpatine as a good man and ob1wan chastizing him cuz of his own distrust of politicians. I sense Palpatine will manipulate and whisper in his ears and capitalize on anakin's own loss.
So in some way or form, in EP 3, Anakin will coem and defeat Dooku in combat. Once he defeats and slains him, he completes his passage into the dark side.
I dont know the reasons for killing dooku. it could be simple revenge.
but those are some rough thoughts. tell me what u guys think.