Sony just teased their Xperia Z4 tablet ahead of the Mobile World Conference 2015 on March 2nd. Sony posted this new photo of the ultra slim device to their Google+ account. The other day we clued you in on Sony's accidental leak of the new Xperia Z4 on their Xperia Lounge app. We surmised that this was ahead of a big announcement at the Mobile World Conference 2015. It looks like we were on track because Sony tagged their latest photo post to Google+ with #SonyMWC.