It wouldn't shock me to see Harper stay in Washington since the Lerners can spend money when need be and even though I nag about it in the GDT threads, we have the makings of a dynasty with our team if everyone stays healthy and comes close to their potential.
If we end up winning a couple of World Series between now and 2018, I think he'll stay. However, if they don't live up to their potential, Harper is as good as gone.