Apart from these 4 unfortunate people, has there been another case, worldwide, reported? I certainly haven't heard of it and in this age of e-gossip it's usually the sort of thing that causes widespread panic and page after page of doom and gloom on every single photography forum and youtube hack video . I'm guessing that it's not unusual for an odd faulty board to get shipped with any camera. Canon will fix them without fuss as they have done in this case in a couple of days, and that will be that.
Of course in an ideal world it wouldn't happen but it is inevitable that it will from time to time. It isn't the sort of thing that people buying an 18 month old camera will worry about . Stuff like this usually fails early on in a product's life and used buyers probably won't care. Of course if it does become a major and real issue, then it's the ones who bought new who will suffer as resale values might theoretically then reduce but we're projecting a fair bit here. I'm confident Canon would take care of any issue as it arose.
It seems to me we're a long, long.long way away from that at the moment and currently. I really can't muster up the energy to manufacture some concern. If it actually does become an issue I have no doubt we will hear about it relentlessly and with full internet outrage. In the meantime I reckon we can relax, enjoy the R5 if you have it, and buy it if you want it.