Topology Research Institute thinks demand is so high for the unannounced iPhone 6 that Apple will sell 80 million units by the end of the year. Assuming the new model, or models, launch in September, that equates to about 20 million iPhone 6 units sold every month for the last four months of the year.
The report assumes Apple will roll out 4.7-inch and 5.5-inch display models, and that the smaller of the two will be the big seller, according to UDN (English translation). They expect the 4.7-inch version to account for some 70 million units sold, and the larger 5.5-inch model will make up between 8 and 10 million units.
Apple hasn't announced or even confirmed the iPhone 6, but there seems to be plenty of information about the iPhone 5S replacement floating around. Along with two larger screen sizes, the iPhone 6 is expected to pack a faster and more powerful A-series processor, better cameras, improved battery life, and a redesigned body that matches the iPad mini and iPad Air.
Reports also claim the iPhone 6 will go on sale on Friday, September 19. Considering Apple's track record, a September launch is plausible and would get the new models on store shelves ahead of the holiday buying season.