With Delta introducing lie flat premium cabin seats on New York JFK – Seattle and New York JFK – San Diego effective April 1 and New York JFK – Las Vegas May 1 current rules are that those flights will not be eligible for elite upgrades. (They’re getting the planes by flying domestic equipment transatlantic from New York to Ponta Delgada, Portugal; Reykjavik, Iceland; and Shannon, Ireland.)
However Delta intends to introduce day of departure elite upgrades for domestic flights with lie flat business class marketed as ‘Delta One’ effective April 1. That will include New York JFK – Los Angeles and San Francisco as well.