Well Facebook might die but I would say it will take at least 5 years, The site is still very popular and has over 1 billion members. Although myspace was quite popular as well at one point and that died very quickly...
MS won't be vanishing for a long time. They still dominate the market with many of their products. If they go, then who will replace them? I think Apple is more likely to die before MS because other than the Iphone and Ipad, there is nothing else that makes them big money and both products are getting old and can't keep selling well forever.