I was in the same boat as you a few years ago. I had worked on .NET for a few years, mostly webforms, because that's just what was available when I got started. I started tinkering around with Python because I needed a load testing tool and found an open source one written in python but it needed some tweaking to work with the viewstate. Anyway, I started learning Python and Django, built a few little sites and webapps just to try it out (ok, I was hoping one of them might take off...they didn't) and eventually a Python dev shop here in town found me on DjangoPeople.net, looked at some of my Django work, and asked me to come in for an interview. Now I'm hacking Python (almost) full time, plus side gigs and personal projects, and I couldn't be happier to only have to look at .NET once in a while.
Maybe there's something to be said for those too lazy to get involved or to try and make a difference. Dave suggested he did get involved, he turned up to usergroups, created new GitHub projects in C#, what did you do?
I'm hanging around because while I don't seem to need the extreme, passionate, awesome, 5-million committer projects to keep me happy, I still contribute something.
I was very wrong.
I'm trying to get out as fast as possible, but applying for a job as a python developer with 4 years of asp.net experience isn't easy.