In this Khador player's opinion, this 'ally' situation has been a long time in coming and makes lots of sense.
Look, all of the Iron Kingdoms can be -- at a root, visceral level -- be divided into two groups:
Non-Living (or anti-Life): Cryx, lesser extent Everblilght
Living (Life): everyone else.
When all are pushed to a brink, it is in all of the Living folks best interests to defeat the Non-Living.
Then we can resume our petty squabbles and games of glory.