The reason that Adobe can do AI gen "out of the box" is because you're paying for it (Firefly).

If GIMP were to implement it, they'd probably have to go the same route as Krita and either spin up or call out to a running instance of Automatic1111 or ComfyUI.

https://github.com/Acly/krita-ai-diffusion

MCP would be cool, but it would be significantly harder than Blender which can represent the "world" as a formal set of expressions. MCP for GIMP would be dealing with layers of rasterized data which would mean integrating with YOLO/LLava/etc in order to make sense of it. It would be neat, but it'd be a daunting integration and potentially VERY VERY slow.