The title hasn't been announced by Warner Home Video yet...not their USA branch, nor their Canadian branch. But Amazon's Canadian site has added a listing
which shows that Teen Titans Go! - Season 4, Part 1
will be coming to DVD on September 12th
That's less than 3 months away, so if the date is correct then we ought to see some official info (and package art!) very soon. For now Amazon.ca only shows the date (and even then you have to scroll down to the "Product Details" section; it's not up top where it usually is). There's no pricing (they're not accepting pre-orders as of this writing), no artwork, and no other details. Stay tuned, though, and we'll update you as soon as we can!