I would suggest the same for the time being: a den leader of a Webelos den should wear a Cub Scout leader neckerchief. However, the uniform inspection form and other documents need to be updated to clarify this. That was the point of my post.
I agree that it does make sense that the neckerchief is eliminated, if the name of the position is eliminated or changed to den leader, however one wants to look at it.
Of course, since BSA uniform parts are not obsoleted by default, a den leader of a Webelos den ought to be able to wear the Webelos den leader neckerchief, if s/he happens to have one. At least, that’s my opinion, based on a conclusion that a modern-day den leader of a Webelos den is effectively the same as a Webelos den leader, the position for which the neckerchiefs were made.