One of the big reasons so separate Cortana from the Windows 10 operating system as a Store app was so it could get updates faster.
The app has just had an update to version 2.2007.9736.0 and ironically one of the elements of the app is that it is now possible to update the app without even visiting the Store.
Just like the new Edge, you can now update the Cortana app simply by visiting its About page (under the ellipses hamburger menu), at which point it will check for, download and install new updates.
Besides the Updating update, it is unclear what else is new with Cortana, with wake words still not supported. At least she can still tell a mean joke, however.