Sony will announce something "slimmer, lighter, brighter" at MWC 2015 - probably the Xperia Z4 Tablet34
As already reported, the Xperia Z4 Tablet should feature a 10.1-inch 2K display (we don't know if this means 1440 x 2560, or 1600 x 2560 pixels, but either option would be nice). Moreover, the new slate should offer "leading battery performance", while being powered by "the latest ultra fast processor." Since Qualcomm recently mentioned that Sony would release Snapdragon 810-based devices this year, we're pretty sure that this "ultra fast" CPU that Sony's talking about is an S810.
Besides the Xperia Z4 Tablet, Sony will also introduce a new water-resistant smartphone at MWC: the Xperia M4 Aqua. Both the Z4 Tablet and M4 Aqua should be officially unveiled on March 2.
As for the Xperia Z4 smartphone, this will most probably not be announced in the next few months (it's said that Sony plans to launch the new flagship handset sometime in the summer). Whatever happens, we'll be here to let you know.
source: Sony (Twitter, Facebook)