If you are traveling over a holiday or a school break, the prices probably won't go down. I have found that Southwest is particularly sensitive to high demand travel times in the local market. The best prices for those times (spring break, Thanksgiving, Columbus Day weekend), are generally found on the very first day the tickets go on sale.
My sister was in the same boat as you last year. She purchased one-way tickets for a cruise out of Fort Lauderdale at a rock bottom price, but declined to buy the return trip since the price for that leg was higher. She waited and watched, but the prices never came down. What she didn't realize was that it was spring break for a local college in her town. Since she didn't have kids college-age, she never realized. Long story short....the prices never did come down and she ended up paying much more for the return ticket than she would have if she had just purchased it at the beginning. So....you might want to do a little research.