Benefits of 8K capture are all the same as 4K capture, you can do a lot of interesting things, especially when your output is a lower resolution. The downsides of 8K capture are of course the overwhelmingly large storage requirements. Broadcasting 8K really only requires the very best of codecs to get the bandwidth down to near tolerable, h.265, VP9, etc. might be able to do this with enough quality that the viewer won't see the compression. But the big question will be, do we need this many pixels? I guess we'll find out during the 2020 Olympics (or before).