Well, that logic is a bit flawed though: you're kind of saying that we shouldn't use a better tool because it may bring us more contributors than we can handle. At the end of the day, we would still use a better tool though.
No, I'm saying that given limited resources, addressing the giant piles of unused code we have (and figuring out how new code won't end up in the attic) seems like a higher priority. Using better tools is always a good idea, and if you'd like to argue that github means patches are less likely to be abandoned that's a good argument to make.
I'm arguing for a broader look at what our development process problems are, and that perhaps efforts should be directed elsewhere.