"iPhone 8 won't be able to buck a trend that's seeing customers increasingly choose older devices, like the iPhone 6s, instead of newer handsets, like the iPhone 7," Fortune quoted Barclays analyst Mark Moskowitz as saying on Tuesday.
Apple has some opportunities to significantly grow in the coming years by investing in India and expanding its services business which includes Apple Music, added Moskowitz.
According to Gartner, in the second quarter of 2016, Apple sales declined in North America as well as in Western Europe. However, it witnessed its worst sales decline in China and Asia-Pacific regions where sales declined 26 per cent.
Apple's much anticipated iPhone 8 is rumoured to sport a bold new design and would feature an OLED display without a bezel.
Samsung and LG, joined by Foxconn-owned Sharp by 2018, are said to be Apple's primary OLED suppliers.
According to earlier media reports, alongside its usual 4.7- and 5.5-inch smartphone offerings, the company would also unveil a third model that would be priced at a higher side than iPhone 7 and would come with invisible home button, all-glass housing, and wireless charging.