On 2 recent coast-coast flights, DL FA's were actively hawking the Delta AmEx cards over the speakers. The FA even went as far as to tell people that they could get separate cards for spouses (instead of a dependent card) and get 50K miles total.
And funny thing, I got the double miles invite from Delta. GF got it from NW, even though she has never flown a NW mile. Both of us are silver on Delta.
Sounds like DL is doing everything to hook people lest they choose to leave with CO. CO must be in a bind between now and before they become part of Star Alliance.
We can only hope that award availability does not get shot over the next year due to this.