Abstract: ‍ ‍By deploying antenna arrays at the transmitter/receiver to provide additional spatial-domain degrees of freedom （DoFs）， multi-antenna technology significantly improves the reliability and efficiency of wireless communication. Meanwhile， the application of multi-antenna technology in the radar field has realized spatial angle resolution and improved sensing DoF. This， in turn， significantly enhances wireless sensing performance. However， wireless communication and radar sensing have undergone independent developments over the past few decades. Hence， although multi-antenna technology has dramatically advanced in these two fields separately， it has not been deeply integrated by exploiting their synergy. A new opportunity to bridge this gap arises as the integration of sensing and communication has been identified as one of the typical usage scenarios of the sixth-generation （6G） mobile communication network. Motivated by this， in this study， we aim to explore the multi-antenna technology for 6G integrated sensing and communication （ISAC）， with a focus on its future development trends such as continuous expansion of antenna array scale， more diverse array architectures， and more flexible antenna designs. First， we introduce several new and promising antenna architectures， including centralized antenna architectures based on traditional compact arrays or emerging sparse arrays， distributed antenna architectures exemplified by the cell-free massive multiple-input multiple-output （MIMO）， and movable/fluid antennas with flexible positions and/or orientations in a given three-dimensional space. Next， for each antenna architecture mentioned above， we present the corresponding far-field/near-field channel models and analyze the communication and sensing performance. Finally， we summarize the characteristics of different antenna architectures and propose new ideas for solving difficulties in acquiring channel state information due to the continuous expansion of antenna array scale and flexible antenna designs.