AGILE and GLAST are the next high-energy gamma-ray telescopes to be flown in space. These instruments will have angular resolution about 5 times better than EGRET above 10 GeV and much larger field of view. The on-axis effective area of AGILE will be about half that of EGRET, whereas GLAST will have about 6 times greater effective area than EGRET. The capabilities of ground based very high-energy telescopes are also improving, e.g. Whipple, and new telescopes, e.g. STACEE, CELESTE, and MAGIC are expected to have low-energy thresholds and sensitivities that will overlap the GLAST sensitivity above ∼10 GeV. In anticipation of the results from these new telescopes, our current understanding of the galactic diffuse gamma-ray emission, including the matter and cosmic ray distributions is reviewed. The outstanding questions are discussed and the potential of future observations with these new instruments to resolve these questions is examined. ©2001 American Institute of Physics.