You do realize that Llano's CPU side is modified K10 tech, right?
Bulldozer itself will be a brand new architecture. The goal with Llano was to integrate a good IGP into the CPU package, hence why they went with the tried and true Phenom architecture to base it on. Why would they risk EVERY new Fusion chip on a brand new architecture? Especially in the sector that makes the most profit for them.
It's a smart move for AMD, they met the goal they were aiming for with Llano, and despite it being 2 generations old CPU tech, it can keep up with the new i3's to an extent, plus has an IGP that absolutely dominates Intel's.