Naturally, as is the case with most of Sony's mirrorless line, the A7R IV is geared toward photographers and videographers alike. You'll get 4K movie-recording with S-Log2/3 and HLG support and, for the first time, real-time Eye auto-focus. Sony's also added a multi-interface shoe for a new shotgun microphone, which is designed to record "high quality" digital sound -- most cameras nowadays capture analog audio via 3.5mm jacks, so this is a completely fresh feature of the A7R IV. Speaking of, connectivity-wise, you'll find access to USB Type-C and dual UHS-II SD card slots.
Other features you're going to care about are the in-body 5-axis image stabilization, 5.76-million-dot UXGA OLED viewfinder, improved dust and moisture resistance and the upgraded grip that should make the A7R IV more comfortable. Compared to the A7 III, you'll definitely notice the difference at soon as you pick up the new camera, since the grip is larger and deeper. At first glance, the A7R IV seems to be a worth follow-up to the A7R III, which is one of Sony's most popular full-frame mirrorless cameras. That said, there are missing features here that some people may wish they had, like a selfie-friendly LCD screen on the back and support for 10-bit video, to mention a couple.
Sony says that when it introduced its super sharp G Master lenses in 2016, it did so with the intention to one day match the performance and image quality potential of its future full-frame mirrorless cameras -- and the A7R IV is that future. We'll be judges of that soon. For now, you should know the A7R IV is set to arrive in September for $3,500 (body-only), while the ECM-B1M digital shotgun mic will be available at the same time for $350.