We explore the potential usefulness of future gravitational microlensing surveys in studying binary properties such as the binary fraction and the distributions of binary separation and mass ratio by using the binary sample detectable through a channel of repeating events. For this, we estimate the rate of repeating microlensing events toward the Galactic bulge field based on standard models of dynamical and physical distributions of Galactic matter combined with models of binary separation and mass function. We find that the total number of repeating events expected to be detected from ～4 yr space-based surveys will be ～200-400, which is ～40-50 times higher than the rate of current surveys. We find that the high detection rate is due to the greatly improved sensitivity to events associated with faint source stars and low-magnification events. We find that the separation range of the binaries to be covered by the repeating events will extend up to 100 AU. Therefore, future lensing surveys should provide a homogeneous sample that will allow investigations of the statistical properties of Galactic binaries unbiased by brightness of the binary components.
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