I will say my opinion about social networks like Facebook, Twitter and Instagram.
I think in future facebook will not be that social network which will dominate a long others.
Now a days, Facebook is the best of social networks, because you can do anything in it, but it is not going for to long to be the best one, because it is dying, other social networks like Twitter are making huge steps to interact with people same goes with the Instagram. In few years instagram will take over every social site just because they're doing everyting to be the best as they can, i don't say Facebook doesnt do it, but they can't make anymore good improvments just because it is not much to do. There are also upcoming new Social sites like Steemit, It will be popular when it launches because you can get paid of making post but it need to changes the websites look, more friendly design, easier to use.
My opinion would be that Instagram will be the most popular social network, twitter will become second and facebook will be third. I think steemit in few years will make it to top10 social site list. Thanks for listening, And have a great day!!!