The M87 supermassive blackhole is thousands of times as massive as Sagittarius A*, but since Sagittarius A* is a lot closer their emission rings appear roughly the same size in the sky (42 μas vs 51 μas). Both have already been imaged by the Event Horizon Telescope. https://en.wikipedia.org/wiki/Event_Horizon_Telescope

We’ve already imaged it with the event horizon telescope. https://en.wikipedia.org/wiki/Sagittarius_A*?wprov=sfti1#