In the olden days of a new social network every other week the percentage of my friends and family on each social network (including Myspace, the most dominant) was relatively low, so the pain of switching was low.
Now the percentage on Facebook is extremely high and I don't even know what an alternative would be.
Lots of friends and family are on Whatsapp, quite a lot of people use Instagram but beyond that... there's very little uptake in any other heavily used social network. And of course, they're both owned by Facebook anyway.
So, for me at least, to say Facebook is on the way out, is something I cannot agree with.