Yes, you're right. Iberia just retired its last DC-10, a type that is now replaced with the A340. The JFK-BCN flight was until now a DC-10. I booked a trip to New York with Iberia last year, I was scheduled to go through Madrid on the outbound segment. I wanted to fly back to Brussels through Barcelona for two reasons: I like the Barcelona airport and I wanted to fly one last time on a DC-10 before they would be phased out. But unfortunately the airline called me to change my flights, going through Madrid instead of Barcelona because I had to go through Madrid to pay the lowest fare. I was so disappointed that I decided not to buy the ticket. I chose instead American which which I had the same fare.
They do still have 747-200's, I saw one in JFK the other day. Those will also be phased out in the near future, the replacement will either be the 747-400 or the A340. But I doubt they will order 747-400's. They will more likely order additional A340's.