Apple is expected to unveil the latest iterations of the iPhone at an event in San Francisco on Wednesday, and while only a minor refresh is anticipated, rumours that the devices will lack a headphone port have created a major flashpoint for iPhone devotees.

Steve Wozniak, who co-founded Apple with Steve Jobs, heads a list of commentators calling the presumptive move a bad idea that could trigger a consumer backlash.

“If it’s missing the 3.5-millimetre earphone jack, that’s going to tick off a lot of people,” Wozniak told The Australian Financial Review last week.

Deutsche Bank analysts in their iPhone preview in July said the headphone jack will be removed in the new phones, which are expected to hit stores on Sept. 16.

Last week, Apple sent media invitations for the event on Wednesday, which is presumably being held to announce handsets dubbed the iPhone 7 and 7 Plus, along with a next generation of Apple Watch.

The invite hinted at an iPhone camera upgrade that may include a dual lens module with an added sensor for improved image quality. Apple declined to comment.

Multiple online images have also highlighted the absence of an earbud jack on the new device, while the Deutsche Bank review said the removal will allow for a thinner and more water-resistant iPhone.

But the move could also upset users, who would have to rely on Bluetooth headphones or headphones that can be plugged into the charging port, while a port adapter may of may not be included in the iPhone price.

“I would not use Bluetooth . . . I don’t like wireless,” Wozniak said. “I have cars where you can plug in the music, or go through Bluetooth, and Bluetooth just sounds so flat for the same music.”

The presumed iPhone upgrade comes after Apple in April reported the first year-over-year drop in iPhone sales since 2003, amid smartphone saturation in some western markets and slowing growth in China. In a research note, Credit Suisse said it foresees “muted” sales increases for the forthcoming models, calling them a “modest upgrade” to existing phones.

A leak from Apple China wholesaler Leleda reported by handset website GSMArena shows Apple will double the storage of the upcoming iPhone models without affecting the price compared to the current iPhone 6S and iPhone 6S Plus.

It says prices for the two new phones will range from $790 (U.S.) to $1,180.

What we might see on the next iPhones:

• 4.7-inch and 5.5-inch models similar in design to iPhone 6S and 6S Plus. Redesigned iPhone with no home button may be on tap for September 2017.

• Larger camera on the smaller model with dual-camera system exclusive to the iPhone 7 Plus. Enhanced zoom and image stabilization features with both models.

• No headphone jack.

• A pressure-sensitive home button.

• Storage capacities ranging from 32GB to 256GB.

• A faster A10 processor.

• More water resistance.

• Stereo speakers and longer battery life.

• A Lightning-to-audio dongle included rather than Lightning headphones.

• Release in some countries on Sept. 16 or Sept. 23.