That sensor is supposedly going to be a 1/1.4-inch (or 0.87 inches if you prefer decimals) Sony IMX903 sensor. That would be about 11% larger than the 1/1.28-inch (0.78 inches) IMX803 sensor you'll find in the iPhone 14 Pro and iPhone 14 Pro Max.
Some Android phones are already getting full-size 1-inch sensors, such as the Xiaomi 13 Ultra. A 1/1.4-inch sensor is still pretty big for a phone camera though, and would still be the largest ever to be used in an iPhone.
Larger sensors are generally better for photos since they can capture more light over their increased surface area, making for brighter and more colorful images. It sounds like this is exactly what the IMX903 sensor will do, assuming it's the same camera mentioned in a previous report on iPhone 15 cameras that can double the amount of light that the iPhone 14 Pro can capture.
Increasing the size of the cameras would, of course, take up more space in the phone. It would certainly explain why the iPhone 15 Pro is also rumored to get an even larger camera bump than the already sizeable one on the iPhone 14 Pro. No doubt this would also be needed to fit in the new 6x telephoto camera tipped for the iPhone 15 Pro Max and the alleged enlarged lenses.
An iPhone 15 Pro Max advantage?
Ice Universe doesn't specify if this new sensor will appear on the smaller iPhone 15 Pro that we expect to appear alongside the Pro Max. The 6.1-inch Pro is already rumored to miss out on the enhanced telephoto camera mentioned above. So if Apple held back another upgrade from its smaller and cheaper Pro, that could prove unpopular with users who want the best available iPhone cameras, but not the larger 6.7-inch Pro Max body.
We'll likely only find out about Apple's new cameras for sure in September, a.k.a. iPhone release month. Apple has launched new iPhones in September every year with only a couple of exceptions, so mark your calendar for just under five months' time.