This happened to us for our trip last Sept. I ended up booking the best flights, then watching - almost daily! - for fare cuts. It was easy to apply the lower rate to my flights, and I ended up with a SW credit for $100 ($50 off each ticket). I think prices dropped twice and I scooped them up both times. My fear about waiting is that either the flights I wanted would be booked up, or that the rates would go up even further.
The only problem with this is you have to be pretty sure you want to travel with SW again within 12 months of your original purchase date or else you lose the credit. Some people roll them over onto new tickets, then change the travel dates on those new tickets- I'm not really sure how that works. It's no problem for us since my folks live in Florida, so we can always send someone down to use up the credit.