Legendary wants a franchise out of this. Remember CHINA owns legendary, so they will have their say.
Dennis is brilliant, but until now he wasn't involved with a movie that's supposed to launch a franchise. BR2 is an independent art house big budget R rated sequel, but that's all. There is no pressure there to make a franchise out of it. Although I am sure deep down the producers would love it to become one.
With DUNE, the pressure will be on to deliver an amazing film that spawns a successful new franchise.