There are not now, nor will there be, plans to remove the regular Ubuntu Desktop as you know it. Ubuntu Core Desktop is being developed in addition to everything else. If you’ve heard otherwise, then that was merely the spreading of FUD.
This has been stated on this very discourse by myself as well as @local-optimum.
So, while we welcome you to this discourse, please don’t believe everything you’ve heard that hasn’t come straight from the Ubuntu community or from Canonical.
With my moderator hat on for everyone else: We will have no further discussion on the topic of the immutable version replacing the regular version (which is not the case) as the previous discussion was closed so that there would be no further uncertainty. Please refer to the previous discussion if you have any questions.