This is currently not on our roadmap. You can retrieve this value by making a call through the Graph API. If this is needed for your scenarios, please continue voting and we will review at a later date.NotSomeoneAtMS commented
This is really surprising and not surprising at the same time with MS.
Who would have thought that it would be difficult in 2018 for an Enterprise ID Mgmt software to send back username in response to a successful request to create one!?
I was able to do hello <%username%> in 1998 without jumping hoops.