will the devs introduce a way to directly upgrade Elementary OS from one version to another when Elementary OS 6 releases?
I also had the same question you are asking, and to solve it, I made a discussion here on StackExchange and on Elementary OS' GitHub Page and also created a issue of it.
Please visit the following links
Many people told me it is not officially possible till now.
GitHub Discussion: There also all I got was disappointment.
GitHub Issue: Status: Closed (Duplicate)
It was linked to this older accepted issue: https://github.com/elementary/triage/issues/46
Thanks & Regards Animish Yadav
P.S. Sorry for disappointment.