[eternauta3k]

Any open source software project will last as long as the community lasts. If interest fades, then it will become worse/harder to run. It slowly becomes incompatible with newer systems, no one is making plugins, documentation becomes outdated.

[imiric]

True, but open source doesn't guarantee that the community will keep maintaining the project, even if there's interest from users. See Atom, etc.

If the main maintainer is a large company, they can decide to shift focus at any point and abandon the project, which puts its existence in jeopardy. (GNU) Emacs and Vim have been around for decades, and they're pretty much guaranteed to be around for many decades to come. As far as long-term investments go, learning and using these is the safest choice you can make.