That would depend. Would it be returning as a sequel or a remake?
The biggest drive for a remake would definitely be nostalgia, but also seeing a good anime with an updated art style and special effects that make it more pleasing to the eyes. These can actually make it more enjoyable than it was at first.
For a sequel, nostalgia definitely plays a part, but the biggest drive for being excited about it would be the fact that it brings a sense of continuation or closure to a storyline that was left hanging. For people that don't read mangas, the return of the Bleach anime next year is godsend.
