The schedule (click here) shows daily nonstop service from ISP to PBI starting on May 19th.
For the same week of May 19th the schedule (click here) also shows daily nonstop service from ISP to FLL.
I didn't look out past those weeks on the schedule but if you click to them then you can browse through successive weeks by clicking on the ">" button. Are you trying to figure out if the flights to PBI will replace the flights to FLL?
Got it. It does look like daily nonstop service is on the schedule between ISP and FLL through June 8th, then the week of June 9th is changes to weekly nonstop service (click here).
I don't work for Southwest so I don't have insight as to whether this is a seasonal change (the daily nonstop service could return during different parts of the year), a test to see if there is a change in demand, a permanent change, or totally unrelated to service to nonstop FLL. Airline schedules are complicated and it would be fascinating to observe the Southwest process!
I did a quick search to see if I could find any press releases or news articles about the direct service from ISP to either airport and came up empty. I am often able to find announcements about destinations but not this time.
If you are so inclined you may want to send Southwest a note with your thoughts about nonstop service from ISP to FLL, this is the link with contact options to submit a suggestion: