Now that I think about it, I see KiB and kb all the time but I don't know that I've ever encountered Kib or kB in the wild. Maybe I'm in a bubble? Or maybe we should accept that kb is power of 10 but kB is power of two?
Well I guess we already basically have this in practice since Ki can be shortened to K seeing as metric prefixes are always lower case and we clearly aren't talking about kelvin bytes.