Sony A7R IV: everything we know so far about Sony's rumored mirrorless camera

Sony may be on the cusp of announcing the Sony A7R Mark IV if current rumors are borne out. This would be the first fourth-generation model in the A7 line of cameras from the company, and an update to the excellent A7R III (pictured above), so we expect it would arrive with some significant updates on what we've seen previously. Here's what we know so far.
Imminent announcement
Image credit: Sony
The company has already made it clear that something is on the way, with a livestream set to begin a