Motivated by recent intensive experimental efforts on searching for
neutrinoless double-beta decays, we perform a detailed analysis of the physics
potential of the experiments based on $^{76}\mathrm{Ge}$. Assuming no signals,
current and future experiments could place a $90\%$ lower limit on the half
life $T^{0\nu}_{1/2} \gtrsim 4\times 10^{26}~{\rm yr}$ and $T^{0\nu}_{1/2}
\gtrsim 7\times 10^{27}~{\rm yr}$, respectively. Then, how to report an
evidence for neutrinoless double-beta decays is addressed by following the
Bayesian statistical approach. For the first time, we present a quantitative
description of experimental power to distinguish between normal and inverted
neutrino mass orderings. Taking an exposure of $10^{4}~{\rm kg}\cdot{\rm yr}$
and a background rate of $10^{-4}~{\rm counts}/({\rm keV}\cdot{\rm kg}\cdot{\rm
yr})$, we find that a moderate evidence for normal neutrino mass ordering
(i.e., with a Bayes factor ${\cal B}$ given by $\ln({\cal B}) \simeq 2.5$ or a
probability about $92.3\%$ according to the Jeffreys scale) can be achieved if
the true value of effective neutrino mass $m^{}_{\beta\beta}$ turns out to be
below $0.01~{\rm eV}$.Comment: 16 pages, 7 figures, the Jeffreys scale used, more discussions added,
to appear in Phys. Rev.