Well I believe that he may change his opininion, not that I want to but anyway, and after he returns from the other dimension Madara will somehow force him to revive him and then Madara might attempt to become the next 10 tails jinjuuriki.
Also there is another prediction, Obito might not change his mind but eventually when he's on the verge of dying he will revive Madara hoping that him would complete their plan.
I will be pretty disappointed if Obito is successfully TnJ'd by Kakashi. But I'd rather that happen then have Kakashi killed off. So maybe Minato and Kakashi will team up together to take down Obito?
I see Obito becoming the 10 tail host. He hinted at it before he went into the other dimension and I really can't see Madara being the only threat left- he doesn't belong in this time, he's a ghost of the past that doesn't share enough bonds or relations with existing characters so to me- it only makes sense that Obito kills Kakashi and returns the 10 tails Jinchuuriki.
Conversion would seem kinda lame, since him and Madara are the two villains that are supposed to be 'truly evil' and unable to change (according to Shukaku at least).