There are no plans for local, on device, in-app folders.
As far as I'm concerned, POP3 is "yesterday", and "today" is IMAP (which provides server folder access). Yes, I know it depends on the email provider, still, that's my view of things.
Easier access to server folders for IMAP (as-needed, rather than syncing all the time) is coming in the next release, development build posted on the forum in its own section.