Go ahead and take a poll of numerous Christians. Ask them what the most important thing is that a pastor does. If you do this, I guarantee that the runaway number one answer will be, "He preaches."
This is a fascinating phenomenon in light of the fact that the New Testament doesn't provide even one example of pastors preaching. Not even one! The sad reality is that the current situation of pastors preaching week after week is based in man's traditions, not in scripture. As they say in the South: it is what it is.
Preaching is the primary way that pastors earn their paychecks. Of course they do many other things, but the primary one is preaching. Just look at the poll results. The main "work" he does is study for hours each week and then preach the sermon(s).
This arrangement guarantees that sermons aren't going away any time soon. The people in the pews believe the pastor should preach, and the pastor needs a paycheck to live. There's a sort of co-dependant thing going on there.
Regardless, the pastor's need to pay his bills is just one more reason that we should not expect sermons to go extinct any time in the near future.