...wich is allowing distant management (with MC I can manage my media collection from my office PC while all my music is nicely stored on a distant server). It's not possible with Calibre.
Of course it is. Calibre has a built in web-server that allows metadata editing, and downloading and reading. Or use remote control.
Although it's true that Calibre has only limited management through a browser, most of its unavailable functionality is functionality that MC doesn't have at all.
... I "hope" that MC will fully replace Calibre
But in a more reasonable point of view, I'm using Calibre only to manage my library. No ebook edition nor creation. I just need to have a place where to store my books, to arrange them nicely in the order I want, to do some basic corrections to the books (wich are mostly fields editions), to look at the nice cover, things like that.
So clearly your concept of management is very different from what I'm talking about.
Calibre has a fully functioning OPDS server, and a HTTP server.
Calibre has a full featured ebook reader, with searching and referencing.
Calibre has a full featured ebook editor, which although not as sophisticated as Sigil, is easily capable of most normal corrections, fixes, and formatting changes.
Calibre has good ebook metadata retrieval functionality, that searches multiple souces.
Calibre has a multiplicity of built-in tools for cleaning up broken epubs.
Calibre has a TOC editor, with the ability to auto-generate TOCs from headings.
Calibre has a very capable ebook format converter.
Calibre has a built-in searcher/browser for getting new ebooks.
And finally, for ebook functionality Calibre doesn't have, it has a plugin framework with a wealth of 3rd party plugins to enhance it.
Comparisons are absurd.
So you just want something to present and list your books, and edit a bit of metadata. That's fair enough, and hopefully MC can get there eventually. But it's not what I'd call ebook management. What you're apparently describing and using is a very small percentage of Calibre's capabilities.