The "one way rate" may be high but it is no different than when it is bought as part of a R/T...and...if one waits until the new fare structure is in place then things might get a bit dicey...
I would almost guarantee that the presently available leg will not decrease in price when both legs are eventually available..but...your choice
Our January SXM trip is usually right between JB availability dates so we are well versed in the one way thing. This year is a first as we were able to book both legs at the same time <img src="http://www.traveltalkonline.com/forums/images/graemlins/Clapping.gif" alt="" /> AND ...both legs are N/S which is a first
The days of R/T fares being lower than two one way fares are gone....(well....unless you are traveling to Europe <img src="http://www.traveltalkonline.com/forums/images/graemlins/Spook.gif" alt="" />)