They had plans for them, they just never built them. They would have been VERY unlike the Superliners, though. They were mostly bedrooms, and big ones at that. I know I've seen the plans for them someplace.There is a reason that Santa Fe never bothered to do any Sleepers in the Hi Level format.
They would have done that around the 1964 second order of the Hi-Levels, and the writing on the wall was getting pretty clear by then.