It seems to me that question is orthogonal to the value of community for a language. If anything, a strong language ecosystem empowers lone hackers, and I suspect most good ecosystems benefit greatly from the contributions of lone hackers.
Not to side-track from programming language semantics, but I hope to engage in a discussion on the sole entrepreneur as you mentioned.
Edit: I think the bottom line of your post and mine is that: No one does it alone. At least, that's my (perhaps more philosophical than technical) take on it. So for hackers and entrepreneurs to reach critical mass with their products/offerings, they need the input/help/support from those around them (family, friends, clients, etc).
I'm fairly sure languages such as Lisp and SmallTalk would be much more widespread today if the industry wasn't told what to use by clueless people driven by profits.
Check out the list of EIGHT GTK+ bindings for Common Lisp:
And yet, the last time I attempted to write a trivial GUI application using GTK and CL, I could not find a single usable library. I tried four and they were all unusably broken on my platform. (This was some years ago. Clearly at least four more implementations have come around since then.)
I think this is a step in the right direction. If the XKCD comic is true that every generation produces a handful of lisp hackers, I hope this is the generation that looks to Quicklisp as a foundation to build a modern, consolidated set of batteries.
Case in point, I recently had an experience where I was trying to read some binary data with nio. This meant I was reading java docs related to nio trying to figure out a java implementation of what I needed to do. Then I needed to translate this into clojure. As a new clojure user who didn't have quite the grasp of the java interop idioms, my code looked pretty ugly, and with a lot of (. foo (. bar (. baz))) looking stuff.
That said, if you're going to have a "problem," a preponderance of usable, high-quality libraries isn't exactly the worst I can think of...