I know there's speculation it's all Disney, but I'm pretty certain it's not, and they've had zip to do with this.
Yeah, Hasbro had zilch to do with this decision...the 6" line is something they have wanted for a long time. Oh wait...
From November 3rd, 2006:
ActionFigs.com: With Hasbro now producing 6" super articulated Marvel figures, could we eventually see a special line with 6" super articulated Star Wars figures?
Hasbro: We have no plans for this type of figure line. As the heart and soul of the Star Wars collecting world, we are focused on making sure our 3-3/4" line is vibrant, fresh, and exciting first and foremost, along with providing continued newness for our other play patterns (Star Wars Transformers, Unleashed 2", and Galactic Heroes).
From December 7th, 2007:
JediInsider.com: There seems to be a decent amount of interest from collectors for 6" Marvel Legends style Star Wars figures. What are the chances we might see a line like that in the future?
Hasbro: We will not be producing a line like this for Star Wars. When we have tried other collector-targeted scales (like 7" Unleashed) we found that fan interest, when compared to the 3-3/4" system, is just not as strong. In addition, for kids, the 3-3/4" scale is also the best one for a wide-range of figures and vehicles that play together, which is critical to the Star Wars fantasy. Rather than spread too thin against collectors, we will be focusing our efforts against making sure the 3-3/4" is broad, as we have been for the past couple of years. We should note that the other sublines - Galactic Heroes, Star Wars Transformers, and Unelashed 2", have a very strong following among kids and we will continue these going forward as well.
So you're right, Disney had absolutely nothing to do with this decision to launch a 6" line and Hasbro was completely blindsided by the 4 billion dollar Disney acquisition of Lucasfilm, which happened overnight. Makes perfect sense.