I could use Elm as it is today for at least a decade without updates, since it's very stable. Anyway, I am sure there are very competent people from the core devs or from the community that could make a new leadership if that happened.
Your assurances don't particularly mean much - no offense. A decade from now I don't want to have a codebase with a toolchain with no future.
There is a contingency plan for that. According to the core team.