The Black Island:
As for the normal version, they are a bit grainy, and the HD remastering will make them look very fine indeed.
I can’t say that I can see an undue amount of grain in the image, either as broadcast, or on DVD, to be honest, but there’s nothing about Blu-Ray which inherently guarantees any improvement in the picture quality: if the limitation is already in the original, if anything it might make it even more obvious.
Cel animations often have a lot of dust and dirt “built in”, as no matter how careful the artists and camera operators are, and however clean the studio environment, particles easily adhere to the images as they are laid on the rostrum. It’s very expensive and time-consuming to clean all of this out, and that’s only if it is actually feasible to do so, as you run the risk of removing details which are meant to be there.
I’m not certain that there will be any major restoration or clean up involved in this release, as I’m not sure it would make the money back.
Frankly I’d worry more about losing the parts of the image they’ll trim to make the “wide-screen” version, as it reduces the picture and can muck up framing of shots, much as the old pan-and-scan process did when going in the opposite direction, for fitting wide-screen movies to a TV screen.