When did you go to UM?
Eaton started out as San Sebastian Hall in the 50s, it was originally all-female (and that's where we got the name for Sebastian the Ibis). Later, when there were more dorms, it was the senior dorm and the name was changed to Eaton Hall. In 1986, the building was renovated and became Eaton Residential College. After my freshman year, it became a popular location, so you tended to have fewer freshmen and more upperclassmen. By 1990s, all of the dorms (Eaton, Hecht, Stanford, Mahoney, and Pearson) were residential colleges, open to all levels of students, and it was that way from the mid 80s until at least the late 90s.
I had heard that they converted Hecht to "freshmen", so it makes sense that Eaton would be for "seniors".
Take a look at Google maps, the new dorms are going up between Eaton and the Merrick/Pavia parking garages. Eaton is staying put.