Neutrinoless double beta (0νββ) decay is the only process which can feasibly investigate the
Majorana nature of neutrinos and total lepton number conservation.
A broad international experimental program requiring considerable resources is being mounted to search for 0νββ decay in the region of parameter space allowed for Inverted Ordering.
The Bayesian discovery probability of future experiments searching for 0νββ decay is evaluated.
A Bayesian global fit is performed to construct a probability distribution for the effective Majorana mass, the observable of interest for these experiments. This probability distribution is then combined with the sensitivity of each experiment derived from a heuristic counting analysis. The discovery probability strongly depends on whether the neutrino mass ordering is normal or inverted, and is found to be higher than previously considered for both mass orderings. In the absence of neutrino mass mechanisms that drive the lightest state or the effective Majorana mass to zero, for the inverted ordering next-generation experiments are likely to observe a signal already during their first operational stages. Even for the normal ordering, the probability of discovering neutrinoless double-β decay reaches ∼50% or more in the most promising experiments.