From Karl Voit, we have this bit of wisdom:

Brodie and Stonebraker define a #legacy system as “any information system that significantly resists modification and evolution to meet new and constantly changing business requirements”.

According to this, #Emacs will definitely never be a legacy system. 😁 — Karl Voit (@n0v0id) January 24, 2020

You can take this in two ways:

Development of Emacs in ongoing and robust. Emacs is infinitely extensible so even in the absence of point 1, you can make it adapt to new situations.

Regardless, until there is a huge paradigm shift in computing, I expect Emacs will continue to be a relevant and useful tool.

Pouya Abbassi also has some appropriate words along the same lines: