San Francisco, Oct 26 : Apple's upcoming next-generation iPhone 15 series will include four models, with bigger feature differences than the iPhone 14 and all the models will feature USB-C charging port, reveals a report. According to AppleInsider, demand for the iPhone 14 range has been rumoured to be lower than expected, and perhaps most definitely for the base model. That perceived failure of the larger iPhone 14 follows reportedly poor sales of the smaller iPhone 13 mini. Yet a new report says Apple will continue producing four models for its 2023 iPhone 15 range. Market intelligence firm TrendForce does not cite any sources, but said the analysis had been made by its Department of Semiconductor Research. "TrendForce indicates that Apple will maintain a four new model release schedule featuring two processors to further differentiate between standard and high-end models," the report said. As per the report, chances are high that the Pro series will feature a memory capacity upgrade to 8GB to match its new processor and continue camera specifications improvements, including upgrading its main camera to 8MP and using a periscope lens in the Pro Max model. The prediction of an increase to 8GB RAM was previously rumoured to be in the iPhone 14 Pro. The move to USB-C has also been predicted, chiefly because the European Union introduced a mandate requiring it. /IANS