Probably not, facebook is the leading social media today. It may still take years or decades for it to become obsolete or if another platform better emerges then facebook will not go down and close.
That is true. Facebook is already a giant in social media platform and it has developed a lot innovated and great technologies as well. I heard they are building a lot of great things also. It is normal for stock to go up and down. I believe it will come back soon later.