There are many 'ifs' involved but 'if' corn could fix its own N like Soys then the consideration becomes is it cheaper than purchasing and applying N.
that is the bottom line but I would probably go the genetic way if the seed cost looked like I would breakeven just because of environmental reasons.

Another reason would be what I forsee coming with regulations about N leaching into the environment and possible/probable regulations on how much you could apply and how you will have to do it by splitting and side dressing at appropriate time etc.
A genetic solution that only fixed as much as plant needed when it needed it could be a great benefit even if it cost a little more for the seed.

It would be something I would keep an open mind about for sure.