They won't disappear, but they'll lose power. FBK will see its power resized due to scandals, but despite them people still prefer it to other social networks by a large margin, and more than a billion people won't drop it due to the network of relationships they established on it.
OTOH MS won't disappear due to its presence in enterprises, but due to competing mobile OS' replacing Windows PCs for many home users, it will receive less money from that market that up until now allowed it to offer enterprises a competitive yet highly profitable product, so it will have to find a less favourable compromise between Windows profits and competitiveness in the business market. It won't disappear anyway, and it will remain profitable, but eventually it won't be able anymore to conquer slices of new markets with the brute force of its huge cash, as divisions losing money to keep or increase market share will gradually become more significant for the company's balance.