NVIDIA CEO Jen-Hsun Huang has gone on record to state that we can expect a new version of Tegra every year, keeping which in consideration we can expect them in the market towards the end of the year or early next year.
As to what Tegra 4 will pack, we will only know for certain when NVIDIA themselves disclose the information, but if the leak found by Chinese site VR-Zone turns out to be true, we could be seeing a few variations of it. One even includes on-board LTE and an A9 architecture, while the rest are all A15 with varied clock frequencies.
VR-Zone also believes that Q1 2013 is the targeted release date.
[VR-Zone (Chinese) via Engadget]