When I was working for big corporates, I was amused that the Human Resources department were very careful when discussing contingency planning to talk of “winning the lottery” rather than “snuffing it”. But it’s a legitimate concern for people concerned with their own investment in the project.
There are nuts and bolts considerations like access to my GitHub account, and TiddlyWiki’s Twitter account. I think we’re in a good position on that.
But at a wider level, I think the TiddlyWiki project would do just fine without me. That’s mainly because I think it has gained a critical mass where it is plausible that for a few years/decades there will be people around who are motivated to improve it.
My own general experience is that personnel changes/additions can often be good for teams, communities or even families. The arrival of new people brings new influences and perspectives. We think we don’t want to see the departure of people but it inevitably changes the landscape and gives opportunities to new people.