For all its flaws (And believe me there were quite a few) I really enjoyed Fable 2, it was fun, sort of immersive and really quite funny at times. And as long as they change very little, I expect I'll enjoy Fable 3 just as much.
But I can't help but wonder where they'll go time-wise. Fable was clearly set in the 1300s, Fable 2 was et in the late 1800s, but where do you go from there? Blackadder went WW1 and the results were brilliant. But something tells me that won't work in an RPG. So the only way they can really go is a direct canon sequel, and that is incredibly dangerous.
People will say "Derp, Rookridge was all grey and depressing in Fable 2, why is it a prosperous suburb to Bowerstone now?"
I will remain wary, keep the gameplay similar and you could be onto a winner, but change too much and you'll kill you franchise. ARE YOU LISTENING PETER?!