Southwest periodically make flights for further in the future available. They’ve added flights until May 8th, 2017 (previously the schedule was only extended until April 24th).
Southwest has a generous refund policy, flights are generally cheapest when the schedule is first released so if you have plans that involve Southwest now is probably time to book (worst case scenario you can cancel/rebook or just use the change flight button to receive a refund that way).
