Frontier have never said they'd release a version of the game that is compatible with offline play, but I think it's unlikely. They decided not to release an offline version initially because it was incompatible with their vision of the game and its mechanics (BGS, shared galaxy, community events, etc.) so I don't think they'll fork the project source now just to strip off all of those pieces. I'm not in their employ, so this is just me talking as a regular player though.
Given that, what will happen is that eventually when Frontier wants to move on, when the game is no longer popular, is not shifting enough units and/or store merch, they'll retire the servers and Elite will become unplayable. That's the deal with always online, games-as-a-service. You can play it only as long as the company decides it's worthwhile to keep the servers on.
So enjoy it while it lasts.
Apparently they did say that they'd release the server application. But I don't believe that.