Since the launch of the iPhone 6 in September last year, it made unprecedented sales for Apple Inc. Quoting a KGI Securities research paper, Apple Daily, a Taiwanese website dedicated to Apple products, stated that the sales of the Cupertino-based tech titan's latest flagship smartphone may not be as strong during the Q4 2015.

According to IB Times, KGI suggests that iPhone sale in the fourth quarter is likely to be somewhere between 65 and 75 million units - a negative to even position for the Apple smartphone. Compared to this, Apple sold 74.5 million iPhones during the corresponding period last year, mainly owing to the pent up demand for the device. KGI envisages the iPhone 6S may not receive the same reception as its predecessor, the iPhone 6, for two reasons - a destabilized Chinese economy and the latest feature of the smartphone - the Force Touch screen, may not be persuasive enough for consumers to upgrade to iPhone 6S.

While China has been cited as the main driving force behind the strong iPhone 6 sales, Beijing's move to devalue its currency on Tuesday may possibly dent the future sales of Apple smartphones.

Meanwhile, Arthus Liao, an analyst with Fubon, told the Wall Street Journal, "China's sudden devaluation confirmed market concerns over China's economic growth," adding, "We expect weaker consumer demand for iPhones in China and Apple may raise its product prices later if China continues to devalue its currency."

Despite the downturn of China's economy, Apple CEO Tim Cook has earlier said that he expects the Asian country to become its largest market in the future.

Incidentally, raising prices of its devices overseas is not something unusual for Apple. According to MacRumors, all through 2015, Apple raised prices in several countries, mainly in part owing to a strong U.S. dollar.

Apart from Force Touch, the iPhone 6S pack an A9 chip, have thicker back case, superior camera and 2GB of memory. It is expected that Apple will announce the smartphone together with new iPads and a revamped Apple TV on Sept. 9.