In reply to Matías.

Matías, that's only true if:
1) a developer can completely turn off access to all other blocks on a page by page (or section/section post/post) bases. Is that the way it's going to work?
2) creating such blocks is easy. From what I've seen so far creating blocks will be very complex compared to meta boxes now

And it still leaves the question open why together with Gutenberg the normal meta boxes have to disappear. Meta boxes are used for many special meta info, meta info that's NOT part of the main content of a page. Think about a real estate website with meta info about each building. Or a job board with meta info about jobs. Meta info and taxonomy info just don't belong in the content (editor). It's not only used to display somewhere, but also to search/filter on in different places.