  This article aims at drawing the attention of astronomers on the ability of
future cosmological surveys to put constraints on string theory. The fact that
"quantum gravity" might be constrained by large scale astrophysical
observations is a remarkable fact that has recently concentrated a great amount
of interest. In this work, we focus on future observatories and investigate
their capability to put string theory, which is sometimes said to be
"unfalsifiable", under serious pressure. We show that the combined analysis of
SKA, Euclid, and the Vera Rubin observatory - together with Planck results -
could improve substantially the current limits on the relevant string swampland
parameter. In particular, our analysis leads to a nearly model-independent
prospective upper bound on the quintessence potential, |V'|/V<0.16, in strong
contradiction with the so-called de Sitter conjecture. Some lines of
improvements for the very long run are also drawn, together with generic
prospective results, underlining the efficiency of this approach. The
conjectures used in this work are discussed pedagogically, together with the
cosmological models chosen in the analysis.
