Wow, imagine being so salty as to want to jilt the father of the franchise, and the whole reason they are getting any money based on it in the first place, simply because they want 100%. Even with Lucas' cut, they would still be making mad-money. Instead, they now have a tottering franchise on the verge of just being 'okay...'
As to the younger cast, I think they had to be there anyway, not so much for story but for the audience. Like the characters, the originals were getting old and younger audiences identify more with their own age group, so having a new and younger cast seems only normal.