I think Emacs users care more about the total population than one particular outmigration.
I don't have actual data, but if I compare to the amount of activity (blog posts, tweets/toots, packages, etc), then (heavy) Emacs usage seems to be monotonically increasing.
Almost everyone I know who switched to VSCode was using Emacs primarily for work, and mostly limited to SW development. That category of users may be large in absolute numbers, but most of the Emacs ecosystem is not driven by that category (i.e. even if that category shrinks to a tenth of its size, it won't have any impact on Emacs development).
Just take a look at the talks in the conference. The vast majority are orthogonal to SW development/programming.