We already know that Samsung is working on the third chapter of the Galaxy Tab series, and it looks like they will be unveiled it in the fall at IFA 2013 in Berlin. This would most likely be at an Unpacked 2013 Episode 2 event, which will obviously feature the unveiling of the Galaxy Note III. We expect to see a 10.1-inch variant along with another smaller variant, around 7 to 8-inches.
There is some bad news for original Galaxy Tab owners in that Samsung will no longer support those devices. As to the Galaxy Tab 2, support will end with the Android 4.2.2 update.