In my weird view, the Steem blockchain benefits from Steemit because it shows businesses just how many transactions they can have on the blockchain at 1.5 seconds and for free. Because of this, Steemit's ultimate purpose is to showcase just how awesome the blockchain is. I don't think Steemit will go by the way side, but even if it did, at that point with many businesses on the blockchain, it would just be like having the training wheels off because all of your steem will be part of a growing business ecosystem.