I don't see a lot of C/C++ developers switching, probably because they have sunk costs with their respective languages and Go doesn't offer very much by comparison.
I would definitely use Go where it seems appropriate, but I don't see it replacing C as a systems language.[0] Sometimes when I write something in Go, I look back and wonder why didn't I just do it in C. However, Go is great in a distributed systems / networking environment where most new code seems to be written.[1]
In the words of a friend, "You can pry raw memory access from my cold, dead fingers."
[0] systems == OS, drivers, etc.
[1] Motivations summarized in the abstract: http://talks.golang.org/2012/splash.article#TOC_1.