With sales of the first-generation Kindle Fire petering out, Amazon is gearing up to launch its successor, a tablet that seeks to improve on the original while retaining a similar form factor. Sources familiar with Amazon’s plans tell AllThingsD that the company hopes to debut the next iteration of the Kindle Fire in the second half of this year; the current launch window is late in the third quarter. To do so, Amazon has been approaching developers to bring them up to speed on the new hardware. Here are a few key changes in the device that we’ve learned about from talking to sources who have been briefed. Read the full story at All Things D.