OK time for some serious speculation about the Khaine: End Times book!

If, as some have suggested, GW are intending to merge the races down into combined races of Elves, Humans etc rather than multiple factions (following the pattern of the Undead Legions and the absorption of Kislev into the Empire) then maybe Tyrion is going to draw the sword of Khaine at some point. This could quite possibly be a result of the death of the Everqueen Alarielle during the daemon invasion of Ulthuan. Many of the Asur have opposed the drawing of the Sword of Khaine so potentially there is a fight between Prince Imrik and Tyrion when he goes to take the sword resulting in Imrik's death. With the Sword of Khaine drawn Tyrion is able to defeat the daemon invasion and become the new Phoenix king. In the meantime Malekith and Morathi are fighting the forces of Valkia the Bloody who has been sent by Khorne to destroy Morathi given her secret place at the head of the cult of Slaanesh in Naggaroth. The Druchii triumph but not before Morathi is forced to reveal herself to be the leader of the cult of Slaanesh to Malekith. This results in a split between them which forces her to flee Naggaroth. That would allow GW to merge Morathi and the Druchii cult of Slaanesh into the wider Chaos book (allowing them to make Chaos Elf characters as well as creating a strong elf theme for Slaneesh).

Tyrion now the Phoenix King of Ulthuan follows the call of the sword of Khaine and leads the Asur armies to war in Naggaroth resulting in a showdown with Malekith. Malekith is killed but not before he is able to unleash a second Sundering in an attempt to destroy Ulthuan and Naggaroth. In order to stop the vortex unraveling Teclis is forced to follow in the foot steps of Caledor Dragontamer adding his power to the existing trapped mages but trapping himself in the vortex as a result. This stops the vortex unraveling entirely but not before Ulthuan is totally devastated and Naggaroth is almost entirely destroyed. With Malekith dead and Morathi fled Tyrion takes control of the remaining elves of Naggaroth effectively reuniting the Asur and Druchii under the banner of Khaine.

With Ulthuan and Naggaroth destroyed or almost entirely uninhabitable a more vicious and cruel Tyrion (having been influenced by the sword) then leads the reunited elves in an exodus from Ulthuan back to the Old World in an attempt to re-claim their lost colonies. This would effectively eliminate Bretonia while bringing them into close proximity with the Asrai. Potentially you then get a show down between Orion and Tyrion (effectively a fight between the Avatar of Khaine and the Avatar of Kurnous) resulting in Orion's destruction by the Sword of Khaine and with Ariel becoming the new Everqueen. That effectively merges Druchii, Asur and Asrai into one new elf faction.

I'm not denying that's some major speculation but this sequence of events doesn't seem impossible or even improbable with a few differences. It would certainly fit the description of annoying people about breaking some of the established lore.