I think the answer is obvious. The concept is proven. The racing is better. Indycar has a good opportunity to replace the DW-12 with a low dirty air focused concept. With front wheel farings and everything. For ovals, it would probably lead to pack racing. So a different aero concept could be used to prevent that.
Low dirty air is all about the road courses. I think F1 on road courses now is more entertaining for this reason. Even vs a nominal spec series. Todays Indycars just don't follow on road courses the way F1 cars do.
With Indycar, the concept would pay even bigger dividends than it does in F1. Just imagine the kinds of racing we'd have. It would be epic.