My Dark Nebula variant uses these changes to the OTU timeline; it is January 5638 AD (late 1117 Imperial), and the focus of the setting is the Solomani/Aslan border; the Imperium is only mentioned in passing as a background. The following things happened in regard to the Imperium:
1) Dulinor took the Iridium Throne directly after the assassination, and is now the titular Emperor.
2) Some Great Houses dissented against his claim to the throne and declared war on him.
3) In 1116 Imperial, the Solomani used the chaos in the Imperium to launch an assault to liberate the old Solomani Sphere. This was called the Eight Month War, and was a decisive Solomani victory, retaking Terra and the rest of the Sphere. The neighboring Great Houses had to sign an armistice with the Solomani, being forced to accept their conquest.
4) The Aslan also won massive victories against the weakened Imperium.
5) The end result is that both polities (Solomani and Aslan) are at the height of their power, and have developed a keen appetite for further conquest. The presence of the Aslan homeworld, Kuzu, as well as the dark secrets of the Dark Nebula, next to the Solomani border, are too tempting to resist; preparations for war are underway on both sides.