When you get to the interview, they will go line by line on your app. One of those questions they ask will be "is this availability date still accurate?" If you can't answer the mail on that one, expect to get the personalized visit with Capt Kraby at the end of the day in the smaller group you don't want to be in. I'd call the Pilot Selection Team, tell them you didn't keep your availability up to date, tell them what it really is, and ask them what to do. Do that, and while they might decide to defer you for a while, you might not get the Delta door shut on you forever. Who knows....I had a friend get hired by Delta almost 9 months ahead of his availability date, so you could possibly even still get to interview.

I don't think you have said how much commitment you have left. If you're Palace Chasing a month or two, that's a different ballgame than a year or two. How much time are we talking about here?