Hi,
As much as I regret it, this project didn’t make it through. I tried to ask the Team to reinstate it and take ownership of a simplified version (because the project scope had gone too far - in my opinion - probably also why it had been abandonned 
) But no luck there at this time (not that I would know).
Instead, there has been an alternate solution that’s been developed by a community member.
https://doc.babylonjs.com/communityExtensions/htmlMesh
However, this isn’t specific to the GUI. So, it’s not really a replacement.
Interestingly enough, the figma to BJS GUI plugin/project (another community project) actually did successfully implement a ‘rich text’.
https://doc.babylonjs.com/communityExtensions/figmaToBabylonJS
So, it definetely IS possible.
Then, if you wanna push for the ‘native’ BJS GUI ‘rich’-textBlock, summoning the Team @Deltakosh @PatrickRyan for version 8 
, know that you already have my upvote 
