  We present a technique-led review of the progression of precise radio
astrometry, from the first demonstrations, half a century ago, until to date
and into the future. We cover the developments that have been fundamental to
allow high accuracy and precision astrometry to be regularly achieved. We
review the opportunities provided by the next-generation of instruments coming
online, which are primarily: SKA, ngVLA and pathfinders, along with EHT and
other (sub)mm-wavelength arrays, Space-VLBI, Geodetic arrays and optical
astrometry from GAIA.
  From the historical development we predict the future potential astrometric
performance, and therefore the instrumental requirements that must be provided
to deliver these. The next-generation of methods will allow ultra-precise
astrometry to be performed at a much wider range of frequencies (hundreds of
MHz to hundreds of GHz). One of the key potentials is that astrometry will
become generally applicable, and therefore unbiased large surveys can be
performed. The next-generation methods are fundamental in allowing this. We
review the small but growing number of major astrometric surveys in the radio,
to highlight the scientific impact that such projects can provide.
  Based on these perspectives, the future of radio astrometry is bright. We
foresee a revolution coming from: ultra-high precision radio astrometry, large
surveys of many objects, improved sky coverage and at new frequency bands other
than those available today. These will enable the addressing of a host of
innovative open scientific questions in astrophysics.
