The F-150 is going to revert back to it's roots: a workhorse for farmers, ranchers, contractors and people who use their truck on a daily basis for doing truck stuff.
However, I dont think you will ever see it be as popular as it was unless the price of gas comes down. As a kid hauler/grocery getter/daily driver; not many people can afford to drive one anymore.
No doubt there will always be people who dont really need a truck but still buy them because they like them, but I believe that Ford's bread 'n butter will no longer be the F-Seres.
I expect that just as the Taurus was once the heart and soul of Ford, its going back to being a car market. I expect that either the Focus or the Fusion (or some midsize car) will be Ford's bread 'n butter.