POTENTIAL JEDI: FALLEN ORDER SPOILERS
Some datamined files from Jedi: Fallen Order over on r/StarWarsLeaks seems to show an image that all but confirms that the Jedi world of Ilum is Starkiller Base. This image appears to be Ilum around the height of the Empire.
Maybe this could be shown on one of the blank view screens in the Emperor’s throne room in ROTJ?