Until they are not... it's still permission, instead of 'always allowed'. I'm quite convinced they will not like it if you make a star-wars themed porn-parody (with the character names as-is) and try marketing it ;)

Lucas was friendly towards fan works, so Disney kind of got that situation handed to them and were smart enough not to go against it. When nerds are your core audience, you have to accept them doing nerd things. WB took down the Hunt for Gollum fan film and ended up reversing course. Would Disney and WB still make a ton of money if they tighten the reins? Probably, but why risk it?