Apple iPhone 6S
Apple's next iPhone could sport a number of new features, while retaining a shell similar to that of the iPhone 6. Reuters

Apple's iPhone 6S could become the biggest rollout ever for the company. Thanks to the popularity of previous models, the 6S could eclipse the records set by iPhone 6 after the new model is released, probably in September, a new report said.

As of March, around 135 million new iPhones had been snapped up worldwide. The number includes the regular-size iPhone 6 and its phablet mate, the iPhone 6 Plus. With little doubt, these two devices headlined the rush by consumers that started in the last quarter of 2014.

The same trend is projected to continue without let-up in the months ahead and will peak only when the 6S is ready to unleash. Analyst Neil Cybart of Above Avalon, according to BGR, is firmly convinced that the iPhone 6S will easily surpass the incredible sales figures registered by the 6 and 6 Plus.

Forecasts from other Apple watchers have been suggesting that the 6S will be loaded with compelling upgrades. The device thickness will reportedly be further shaved off and the rear camera will be bumped up to 12 megapixels. Also, the Force Touch sensor that was part of the Apple Watch will be on board and the tandem of the iOS 9 operating system and A9 chip should bring the device into full life.

By Cybart’s reckoning, Apple will ship 230 million new iPhones in fiscal year 2015 and another 250 million in fiscal year 2016. Within that span the Cupertino, California, tech giant will further pad its cash haul as the 6S becomes the dominant player, the analyst said. If Cybart's estimates are correct, more than 350 million existing iPhone users will want to get the iPhone 6S and 6S Plus once they arrive.

That estimate includes many users of early iPhone models who weren't enticed by the iPhone 6 and 6 Plus. But many will take the plunge with iPhone 6S, according to Above Avalon. The Above Avalon data also indicated that, to date, there are around 475 million active iPhone users across the globe. If Cybart's forecasts hold, the iPhone 6S could easily double that figure.