Yes - if any disount comes out that makes the price of the cruise go down we will apply it automatically. You will get the lower rate and you will still be invited to all of the PodCast parties, eligible for all giveways, etc (as long as you are still booked through DU - but there is no reason you wouldn't be).
Of course any reduction in rate or discount will have no affect your shipboard credit. That is linked to your stateroom category, not the price, so even if your price goes down you still get the shipboard credit from DU.
John