  We reconsider the QCD predictions for the radiative decay $B\to \gamma \ell
\nu_\ell$ with an energetic photon in the final state by taking into account
the $1/E_\gamma, 1/m_b$ power-suppressed hard-collinear and soft corrections
from higher-twist $B$-meson light-cone distribution amplitudes (LCDAs). The
soft contribution is estimated through a dispersion relation and light-cone QCD
sum rules. The analysis of theoretical uncertainties and the dependence of the
decay form factors on the leading-twist LCDA $\phi_+(\omega)$ shows that the
latter dominates. The radiative leptonic decay is therefore well suited to
constrain the parameters of $\phi_+(\omega)$, including the first inverse
moment, $1/\lambda_B$, from the expected high-statistics data of the BELLE II
experiment.
