I surely hope not.

Miles are a liability - an expensive liability to keep on the books, and that is bad for the airline.

Furthermore, having non-expiring miles devalues the miles significantly, potentially making it much harder to make good use of them, and that is bad for the consumer.

Expiring miles are a lose-lose, especially considering how freaking easy it is to make sure your miles don't expire (Step 1: Log into AAshopping. Step 2: Spend 99 cents on iTunes).

Delta SkyPesos are worthless as is, and they just became even more worthless by making them non-expiring, keeping potentially millions of miles that would have otherwise expired floating in circulation for people to redeem on awards that will now become even more difficult to find.