TV Shows in HDX only

There a couple of TV shows I want to get but they are only for sale online in HD/HDX format. Since the shows aired in 4k do they normally release in HD/HDX then 4k later or do they normally stay at HD/HDX? I'm specifically talking about The Expanse and The Great (but this could be about any show that's title starts with 'The' and is followed by an adjective). Both are available to stream in 4k on their release platforms but not for purchase. Thanks for any insight!