In reply to Matías.

I really, really hope this is true. I have about 70 active websites for clients, using all kinds of meta boxes, some from plugins, most with some custom code I have build. From a simple couple of form fields to fill in meta info for a page to pulling in a google map to let a client pick a location. Even now building a couple of websites using custom post types and meta boxes. All small clients, who will not be able or willing to pay for a sudden need to rebuild things.

I'm fine with things improving and new possibilities to build things. I'm not opposed to change. The way I build Wordpress sites now is different from five years ago. But the thing is, there needs to be no sudden breakage and enough time (many years) to transition code bases.