I always suggest if you want it, book it. Right now could be the best deal going. And if you wait to book and they don't offer anything, then what?
But to answer your question, basically no, they don't have too many short term 'flash' sales since they don't cater to the mass-market crowd.
Here's the latest they're offering on the Navigator;
• 2-for-1 Fares
Bonus Savings of up to $3,500 Per Suite
Unlimited Shore Excursions
1-Night Pre-Cruise Luxury Hotel Package
Pre-Paid Gratuities • FREE
Unlimited Beverages Including Fine Wines and Premium Spirits