  Optical long-baseline interferometry is a unique and powerful technique for
astronomical research. Since 2004, optical interferometers have produced an
increasing number of scientific papers covering various fields of astrophysics.
As current interferometric facilities are reaching their maturity, we take the
opportunity in this paper to summarize the conclusions of a few key meetings,
workshops, and conferences dedicated to interferometry. We present the most
persistent recommendations related to science cases and discuss some key
technological developments required to address them. In the era of extremely
large telescopes, optical long-baseline interferometers will remain crucial to
probe the smallest spatial scales and make breakthrough discoveries.
