It all depends on what Apple does with the extra space. If they choose to cram the sensor with more and more pixels, quality will not be as good as a larger sensor with larger or less pixels.
More pixels will give you higher resolution but larger pixels will give much better low light quality with less "noise". If you hate that "noise" in lower light images then larger pixels is the way to go!
There is a compromise no matter which way Apple goes.
Oh dear, I sense something akin to the old megapixel debate rearing it’s ugly head
This is actually a hugely complex matter. Bigger sensors, should mean better quality, but only if the sensor is designed for it.
Smartphone sensors are ridiculously tiny in the grand scheme of things. So quality is incredibly important. As has been mentioned, simply stuffing more pixels in isn’t necessarily the best way to go.
Light is one of the most important aspects of photography, specifically, capturing light.
With the tiny sensors in smartphones, which can sometimes be as small as around 5mm x 4mm. Having bigger pixels to capture more light makes much more sense. If that is, you want to place quality over resolution.
If Apple use a larger sensor, I hope they go for larger pixels. It’ll produce better images, especially in low light situations.
Of course there’s all kinds of trickery that can be used these days, some of which Apple already do. Capturing multiple images and combining the best of them. Capturing the image simultaneously in true black & white, then using those captures to improve light balance without noise and so on and so on.
Just look at what Google can do with one camera to see what’s possible with intelligent image manipulation. AI like that with bigger sensors and more cameras, could produce really good results.
Last but by no means least, the single most important aspect of a camera - the person holding it. Good photographers can produce amazing results with even the most basic of cameras.