According to a report from ETNews, LG Display is collaborating with Lenovo to develop a foldable tablet. The tablet will use a 13" foldable OLED - which LGD aims to start producing in the second half of 2019.
The 13" display will be around 9" when folded. So this device will stay in the tablet size category when folded, this will not compete in the smartphone market. This is the first time we hear of such a device under development - which could make sense as a tablet is not used as much as a smartphone is - and so the number of supported folding cycles can be lower.
In December 2016 Lenovo demonstrated two foldable device prototypes, including Folio, a tablet that folds in half to be an edge-type smartphone (this is not the same device type which is reportedly under development). You can see the Folio in action in the video above.