Honestly, I'm still trying to find out what the appeal for 3D Graal is..
You have a valid concern.
It will just divide the already dwindling player base as players leave one Graal game to try out the new ones. Not to mention the new 3D games will not have close to the amount of content, items, etc to match the existing content in the 2D games.
Also the 3D mechanics offered in the 3D versions are not enough to set it apart from other 3D games on the app store. Development costs of a 3D game are much higher and has a higher learning curve for new artists who might want to help contribute. (Which is much easier on a 2D game)
As much as I want a successful 3D Graal game, if they do release it will be detrimental to the community and Graal IP.