The potential is in flexibility. Phones are small. Tradeoffs are substantial. Some people would prefer 50% more battery life at the expense of the camera or weight. Maybe someone can make an e-ink screen that will double battery life. Some people might want to spend $800 on the camera.
IMO, that's the benefit.
Commercially, I see this as something can keep buying add ons to. The market of people who buy 2-3 pricey covers for an ipad is legit. People like their phones and add ons might sell because people will just want to buy new things for them.
In that sense, maybe this will extend life a little or partially as you take some old modules with you, but that's not the point. The point is can flexibility let people make a phone they like better and enjoy doing it.