You can make templateName a property and then work out what template to use based on the content.
For example, this uses instanceof to set a template based on the type of object:
App.ItemView = Ember.View.extend({
templateName: function() {
if (this.get("content") instanceof App.Foo) {
return "foo-item";
} else {
return "bar-item";
}
}.property().cacheable()
});
Here’s a fiddle with a working example of the above: http://jsfiddle.net/rlivsey/QWR6V/