This question puts me in an awkward position. I don't want to discourage you from using Beautiful Soup, but if the long-term future of your software dependencies is a major concern for your architecture, you should try pretty hard to minimize those dependencies. If you need an HTML parser, you should use html.parser, since it's part of the Python standard library and comes with a long-term support commitment.
Most open source projects have solo maintainers, not just Beautiful Soup. I don't think it's terribly unusual. I've collaborated with many developers over the years, like Isaac Muse (maintainer of Soup Sieve) and Stefan Behnel (maintainer of lxml), but we've mostly worked through the interfaces provided by our separate software packages.
One way to manage the risk of relying on solo maintainers is to have your organization sign up for
Tidelift. Maintainers who participate in Tidelift, including myself, commit to various best practices that I think will address some of your teammate's concerns. I don't want to turn this into a sales pitch, so look at the Tidelift website if you're interested.
As for a plan, Beautiful Soup is 20 years old and quite mature; I don't have any plans for significant new development. My main goal is to keep Beautiful Soup in a state where it would remain useful for 5-10 years if I were to die or stop working on the project. This mainly involves keeping it up to date with recent versions of Python.
Leonard