Right, then we're not talking about WotC.What is someone did a Kickstarter? Also, I do not agree that its a guaranteed money loss.
As has been said, DM's Guild or 3rd party publishers in general are your best bet here.
I'm sure you could find someone doing a small scale project out of it.
WotC won't though. Only one adventure currently supports levels 16-20. There is a lot of room for support for those upper levels but there probably isn't the demand for it. I imagine we will continue to see a trickle of support for 16+, basically every now and then as they saturate the lower levels.
The demand for 21+ is minuscule. I don't think it will ever happen.