Yep, Cadia broke, but there still are forces fighting in the system.
On a different note, with people talking about AoS, one of the things I like about it is the variety of armies that you can make. Fantasy was restrictive in terms of how much of a unit type you could take. In AoS, you do need a certain number of Leaders and Battleline units, but the units considered battleline can change by taking certain heroes and sub-factions.
For instance, every non hero Flesh-Eaters Courts units can become battleline through one option or another. This includes the giant undead bats and dragons.
Pretty much every chaos book is at least two armies in one; mortal and daemon. And those armies can mix with themselves, beastmen, and sometimes skaven.
This method of army building allows players to truly make “your dudes”.