I've checked all the adapters and return values for their methods. All of them return Promise already as effect of adandoning jQuery.Deferred in earlier releases.

I've also checked docs and they are in good shape.

I've noticed that indexeddb/ecrypted tests are not run, probably because of PhantomJS that does not support IndexedDB.

I think we are fine in terms of ES6/Promises compatibility /wrt DataManagers.