Yes, Amazon updates its Kindle e-readers every year, so it's kind of a given that a new model is coming this fall. This year's refresh may actually be interesting, though. According to The Verge, the next model will be called the Kindle Voyage, and it will feature a 300 PPI screen.
300 PPI would represent a 42% increase in pixel density over the Kindle Paperwhite, whose 6", 768x1024 e-ink panel yields only 212 PPI. The Verge says the Kindle Voyage will stick with the same 6" display size, so I guess that means the resolution will wind up somewhere in the neighborhood of 1440x1050. The extra pixels should do wonders for font rendering, which isn't the Paperwhite's current strong suits.
This information comes from premature listings on Amazon Germany and Amazon Japan, so it's probably legit. The Verge even snagged a picture of the Kindle Voyage from an Amazon manual. The shot shows a device not unlike the current Paperwhite, but with a thinner frame and sensors on the left and right parts of the bezel. Apparently, the sensors will let you turn pages by "pressing lightly on the bezel." The Kindle Voyage is also supposed to be slightly thinner and lighter than the Papwerwhite. According to Amazon Japan, it will be 8-mm (0.31") thick and weigh 186 g (6.6 oz), down from 206 g (7.3 oz) and 9.1 mm (0.36") for the Paperwhite.