Never going to happen unless AA and DL do the same thing.
Otherwise UA raises to $25k, DL and AA run status matches for people who spend $12-25k, and the head of loyalty programs at UA gets fired when they suddenly lose a ton of people spending not insignificant amounts of money to their competitors.
$15k to match DL would be reasonable since it doesn't put them at a competitive disadvantage but 25k would be stupid, they'd be better off devaluating benefits.