As the tech community’s expectations for the iPhone 6 continue to heat up, one firm thinks estimates for the handset’s volume sales could be too low. BlueFin analysts John Donovan and Steve Mullane already expected Apple Inc. (NASDAQ:AAPL) to beat the guidance it provided for handset sales this year. Now they are increasing their own estimates because they expect major upgrades to spur increased demand with this upgrade cycle.

iPhone 6

Rumples of “massive” iPhone 6 builds

The analysts said sentiment that Apple Inc. (NASDAQ:AAPL)’s iPhone sales estimates are conservative has become more widespread. Their research suggests that the iPhone 6 will launch in September, as many others have suggested. They’re projecting that most sales activity on the handset will take place during the fourth calendar quarter.

They note that estimates for iPhone 6 sales range from 45 million up to 70 million units. Despite the high end of that number, BlueFin is raising its estimates for the handset to more than 55 million units, keeping even this bullish firm from topping previous analyst estimates.

iPhone 6 to finally break the mold

The analysts at BlueFin note that the transition from the iPhone 4 through the iPhone 5 “offered little differentiation” among the handsets, which kept upgrades lower. However, they see rumored major upgrades for the iPhone 6 as being a game changer this time around. For the full 2014 year, they’re estimating that Apple Inc. (NASDAQ:AAPL) will sell 174 million iPhones. They say their mix of “iPhone 5 vs iPhone 6 is changing,” with no mention of the iPhone 5S, although their overall number is remaining the same.

They see a “white hot opportunity” for Apple Inc. (NASDAQ:AAPL) this year not only because they expect a major upgrade this time around, but also because of lackluster reviews for the Galaxy S5—the iPhone’s biggest competitor. They think that “the combination of the correct product mix and the advent of lower cost options and relaxation from carriers relative to upgrades/ refreshes should translate into solid momentum for the iPhone” as this year progresses.