It appears that Sony Mobile is looking to add a new Xperia tablet to the family, following a post on an Indonesian site showing a new tablet with a model number of SGP621. The model number suggests that the tablet will sport LTE and continue the line of Xperia Z tablets with the LTE Z2 and the Tablet Z sporting model numbers of SGP521 and SGP321 respectively.
Other rumors have Sony readying a smaller tablet and this could possibly be that said tablet. Given the timing of the post, there's a chance that we'll see the device debut at IFA this year. The conference starts on Wednesday, Sept. 3.
source: Xperia Blog