Ah, well we'll see
I still think of calibre as a conversion tool. And most calibre users are ebook consumers rather than producers. But if people want to use it to prepare books for publication, more power to them.
Adobe also recommend calibre for converting the output of InDesign to MOBI.
I'm actually planning to write a small tool in calibre to fix common problems in EPUB files to make it easier to create publication ready EPUB files.
At this point, the only big company that doesn't recommend calibre is Amazon, in fact, I believe they send emails to people that submit calibre created books warning them not to use calibre.