I was reading an article from the show runners of Prodigal Son. They had an ending in mind right from the start of the season, and they ended up shooting the finale out of order. Then they went back to their normal schedule. So when it became clear that the virus was going to impact filming. They revamped ep 17 to make it fit the finale and basically scrapped 18 and 19.
I wish SPN had done something like that. I'd rather have a definitive ending even if it meant 2 or 3 less eps. Given that nothing has really happened all season, I don't see it being that hard.
I know they all want to film the ending, and I know they will do everything in their power to to do so, but nothing is guaranteed. If for some reason it doesn't that means the shows legacy ends on a (not sure if writers for eps are spoilers so tagging just in case.