I like to think that lessons have been learnt from the openings of DLP, WDS, DCA and HKDL. Though i have not been there Shanghai DL does look great and the expansion of DCA has been amazing.
But in terms of 3rd park based on European folk lore etc i just cant see it happening, i cant even see it happening in the Disneyland park.
If they expanded WDS with Star Wars, Marvel etc and put journey to the centre of the earth in where star tours currently is i think it could happen and I would be so, so happy because you are right their is so much to create from the European cultures, myths, legends etc but i dont see it happening.
I feel like Disney would see it as more need and cost effective to throw IP's at Paris because of the debt and cost of purchase the resort.
This is not me saying its a bad idea, I would be so happy with an EPCOT style park with an emphasis on the worlds showcase section but i dont think that is particular popular with casual visitors, though i would love a maelstrom ride and a Matterhorn