This is actually quite likely to happen - Mass producing a rooftop tile with integral solar cells and slot-in connection with all neighbouring tiles is doable industrial engineering, and I dont see any inherent reason why this would be that much more expensive to put up than a conventional roof. Which would make them universal on new build and renovations where the roof needs replacing regardless. Retrofits..
Ever had to have a roof replaced? Not cheap. Not cheap at all. So this would scale up very, very slowly as roofs are replaced at the natural rate.