There are 5 737-800s in their fleet that are older than all their remaining -300s. You wouldn't know it though. All are in very clean, tidy condition. I suspect the new order fits in well with B757 retirements then upgrading -800s which will then backfill -300s as they are retired. Then they can balance the fleet with early -800 retirements as they need to to manage fleet size. I suspect even though the new ones are coming, other than 737 and -300 retirements, the eventual fleet size is anyone's guess....