Ability to define multiple states for a component or group based on certain conditions. For example, you could make a button with two states. A green button if the value is True and a red button if the value is False. Each state can have their own sets of actions. Currently this kind of interface can be set up using the Change Visibility feature, but states will make this much easier.
This will likely also include a new action to Change State, so that states can be changed on click (tap) or hover.