Let’s hope so, but color me very skeptical. But I reckon e. g. a 1x12 GRX-based setup with larger chainrings could be quite popular with road cyclists, too.
A cynical take on Shimano’s decision for a mechanical 1x12 groupset is cost: they still haven’t released 12-speed Di2 MTB groupsets, and it might cost them more than to modify a mechanical groupsets to accommodate 12-speed cassettes. On the road side, I think their incentive is to push the average price up. IMHO releasing a mechanical 12-speed 105 or Ultegra groupset would all but kill 105 Di2.