Another thing with such niches is fragmentation. The niche might be really small, but there are often more than one project. In this case gEDA and KiCAD, and a few other even smaller projects. Each suffering from a lack of developers and other resources.
Imagine what could be done if gEDA and KiCAD would join forces. It isn't very likely to happen, it rarely happens with other fragmented free software projects. But it would be great.
And regarding gEDA, they do make strange project decisions. Some years ago they got some funding as part of Google's Summer of Code. Instead of using that to improve one of their flagship tools, gschem or PCB, because these tools need it, they did some Verilog stuff.
I don't believe hoards of developers will show up in the future. Especially not from the Arduino movement. For that a project needs to be approachable on multiple levels. Starting from being easy to just build from the existing code base, to being able to get small changes accepted into the project in reasonable time, to setting the right, attractive priorities, giveng developers a sens that their work matters.
And the Arduino guys? They want it to be easy and simple, with a lot of hand holding and back rubbing, without having to put in real hard work. And their knowledge in doing real programming ... I wouldn't count on them as a large future source of developers.