No, not really. Many runners do the races as part of a normal vacation and have their park plans set up just like everyone else. Those who will visit the parks tend to go back to their rooms and change before going out so just having a race finish at Epcot doesn't play into which parks people do visit. Only on Sunday, with the half finishing after the park opens will have a bit of different feel, and with the after party Sunday night, Epcot will be more crowded in the early evening (party guests can get in to the park at 5:00). Since it is Food and Wine, Epcot will already be really crowded in the World Showcase on Saturday and Sunday afternoons.