  We predict the range of proper motions of 19 satellite galaxies of M31 that
would rotationally stabilise the M31 plane of satellites consisting of 15-20
members as identified by Ibata et al. (2013). Our prediction is based purely on
the current positions and line-of-sight velocities of these satellites and the
assumption that the plane is not a transient feature. These predictions are
therefore independent of the current debate about the formation history of this
plane. We further comment on the feasibility of measuring these proper motions
with future observations by the THEIA satellite mission as well as the
currently planned observations by HST and JWST.
