This has already started to a degree, as people trying to build net-zero homes find that at a certain point the cost (in money/effort/carbon/energy) to add further insulation exceeds the cost of adding heat to the home via adding solar PV. I believe retro-fits of older homes hit this point earlier, since it can be harder to insulate them beyond the low hanging fruit.

Obviously as PV price continues to drop, this point will be met earlier and earlier.