Ideally we will someday find a way to get it to work but there is no current planned release for supporting rich text editor.
I don't know of any workaround. The problem is not an easy one to solve. The issue is moving an iframe. IG works by moving controls in and out of the cells. Rich Text Editor uses an iframe. Moving an iframe tends to destroy the content.
What you could try is putting the RTE in an inline modal dialog region then in the cell put a button that opens that dialog along with code to move the edited value in and out of the model.