It is probably not a a 20 inch 4K OLED.
"Some web sites are reporting that Panasonic is set to unveil a 20" 4K OLED tablet at the IFA 2013 event next week. Those sites are relying on auto-translated Japanese text. But in fact the company will not show such a tablet. In an English PR, Panasonic says they will show a 4K 20" tablet and a 4K OLED panel prototype - those are two different devices."
Thanks for this info. I should probably remove my post with the article given that it's totally wrong...