If you're talking about the fact that the SD card is now part of the file system, not an external storage device, that has nothing to do with the file manager apps. It has to do with learning how Linux works, so that you can create folders using the apps that are going to write in them. You can't create a file with one app, then edit it with another app, unless the editing (renaming, deleting, any edit) app is a member of the group that created it or is rooted.
That's not going to change with 5.0, 5.1, 6 or any later version of Android. It's been that way in Linux ... well, in Unix, from the beginning, and it's how most operating systems (not Windows or Mac, but most real ones) work. It's how Android should have worked from the start.