Ok, maybe not a tribute to the F4 in the sense of a celebration, but certainly a tribute to its features and their implementation. Consider these external controls that exist on both cameras:
P, S, A, M - mode selector
EV compensation dial
S, Cl, Ch, Cs (Q), s.t., frame rate selector
the usual shutter speed, ISO, and AF mode controls
An F4 user would find the Df very familiar and vice versa.
Aside from the Df and the Fuji X cameras, you just don't see that many dedicated external controls on a single body among contemporary cameras.