  We examine the potentially very promising signal $B_s\to \mu^{+}\mu^{-}$ in
supersymmetry with large $\tan\beta$ in a {\em top-down} approach starting from
the best fits of an SO(10)-like model studied recently. Our results go beyond
minimal flavour violation investigated in previous works. We show that the
absolute best fits provide a signal for $B_s\to \mu^{+}\mu^{-}$ at the
borderline of the present limits and hence the ongoing search at the Tevatron
will start having an impact on the global analysis of this class of SUSY
models. We discuss the implications of a measurement of $B_s\to \mu^{+}\mu^{-}$
for restricting the parameter space of gauginos and sfermion masses, and of
signals in other channels $B_{d,s}\to l^{+}+l^{-}$. We also discuss
correlations of $B_s\to \mu^{+}\mu^{-}$ with the CP-odd Higgs mass, $\sin
(\beta -\alpha)$ and $b\to s \gamma$ in SO(10)-like models.
