Leak artist @evleaks has put his hat into the ring into the purported Xperia Z3 (D6653) specifications. Judging by his very good track record, they are probably quite accurate too. On the face of it, the hardware spec-sheet reads very similarly to the current Xperia Z2 flagship.
This includes a higher-clocked processor in the form of the Qualcomm Snapdragon 801 chipset (2.4 GHz quad-core Krait 400 CPU and Adreno 330 graphics). We are most likely looking at the MSM 8974-AC chipset, versus the MSM 8974-AB chipset currently found in the Xperia Z2.
Other specs include a 5.15-inch display with 1080p FHD resolution, 3GB RAM, 16GB internal storage, a 20.7MP Exmor RS rear camera, a 2.1MP front-facing camera and it will launch with Android 4.4.4 KitKat.
So yes, on the face of it in terms of hardware not much has moved in. Perhaps this is where integrated wireless charging comes in?