  Ultralight bosons can affect the dynamics of spinning black holes (BHs) via
superradiant instability, which can lead to a time evolution of the
supermassive BH shadow. We study prospects for witnessing the
superradiance-induced BH shadow evolution, considering ultralight vector and
tensor fields. We introduce two observables sensitive to the shadow
time-evolution: the shadow drift, and the variation in the azimuthal angle
lapse associated to the photon ring autocorrelation. The two observables are
shown to be highly complementary, depending on the observer's inclination
angle. Focusing on the supermassive object Sgr A$^\star$ we show that both
observables can vary appreciably over human timescales of a few years in the
presence of superradiant instability, leading to signatures which are well
within the reach of the Event Horizon Telescope for realistic observation times
(but benefiting significantly from extended observation periods), and paving
the way towards probing ultralight bosons in the $\sim 10^{-17}\,{\rm eV}$ mass
range.
