  At the dawn of the next-generation wireless systems and networks, massive
multiple-input multiple-output (MIMO) has been envisioned as one of the
enabling technologies. With the continued success of being applied in the 5G
and beyond, the massive MIMO technology has demonstrated its advantageousness,
integrability, and extendibility. Moreover, several evolutionary features and
revolutionizing trends for massive MIMO have gradually emerged in recent years,
which are expected to reshape the future 6G wireless systems and networks.
Specifically, the functions and performance of future massive MIMO systems will
be enabled and enhanced via combining other innovative technologies,
architectures, and strategies such as intelligent omni-surfaces
(IOSs)/intelligent reflecting surfaces (IRSs), artificial intelligence (AI),
THz communications, cell free architecture. Also, more diverse vertical
applications based on massive MIMO will emerge and prosper, such as wireless
localization and sensing, vehicular communications, non-terrestrial
communications, remote sensing, inter-planetary communications.
