  The survey of the inner Galaxy with H.E.S.S. was remarkably successful in
detecting a wide range of new very-high-energy gamma-ray sources. New TeV
gamma-ray emitting source classes were established, although several of the
sources remain unidentified, and progress has been made in understanding
particle acceleration in astrophysical sources. In this work, we constructed a
model of a population of such very-high-energy gamma-ray emitters and
normalised the flux and size distribution of this population model to the
H.E.S.S.-discovered sources. Extrapolating that population of objects to lower
flux levels we investigate what a future array of imaging atmospheric
telescopes (IACTs) such as AGIS or CTA might detect in a survey of the Inner
Galaxy with an order of magnitude improvement in sensitivity. The sheer number
of sources detected together with the improved resolving power will likely
result in a huge improvement in our understanding of the populations of
galactic gamma-ray sources. A deep survey of the inner Milky Way would also
support studies of the interstellar diffuse gamma-ray emission in regions of
high cosmic-ray density. In the final section of this paper we investigate the
science potential for the Galactic Centre region for studying energy-dependent
diffusion with such a future array.
