To be honest, I think Steemit will be more than just a platform as it is literally bootstrapping a Digital Economy. Within our life time, you'll see Steemit become much bigger than Facebook, Twitter or any other Social Platform   but who knows there is always a chance of different platforms becoming more popular. Personally, a lot of people hope for Steemit to succeed because this a never done before experiment that is actually distributing value among its community member quite well. You don't have to invest money, nor are you forced to enjoy the good free content on here since what you do with your life is your choice, so you decide what you wanna spend your time on