8 year old technology that the Tegra 3's GPU is based on. Speculation is that NVIDIA's new Kepler GPU architecture will be included in the Tegra 4. This architecture is currently found in desktop video cards and in the GPU on notebook computers. While this is still just speculation, if Kepler makes it into smartphones via the Tegra 4, it will allow the latter to carry 32 to 64 GPGPU-compliant Kepler cores inside.
Kepler architecture offers improved performance including better power consumption. And according to Android Authority, the competition in the form of ARM's Mali-T600 and Imagination Technologies' PowerVR SGX54x is no match for Kepler.
The NVIDIA Tegra 4 is also expected to feature a Icera baseband modem. While we should see the Tegra 4 in consumer products by the end of this year, it won't be widely available in the consumer tech market until Q1 of 2013.
source: VRZone via AndroidAuthority