Most of the Microsofts revenue comes from server side stuff anyway, 60% from memory(?), it'll be a good 5 years at least before that market dents. I don't think you'll see c# going away anytime soon.
EDIT : couldn't find 2012 but heres 2011 http://punchcut.com/sites/punchcut.com/files/win8_1-8_eb-msf... business + server looks around 60% which I guess is where my figure comes from