https://ir.spirit.com/resources/fleet-plan/default.aspx

Stating the obvious to some of you here.
Spirit has always said that any of the 320 series orders can be executed as 319 or 320 or 321, but as of now the fleet plan specifically shows only 320neo and 321neo orders.
I don't recall ever seeing any specific 319neos in the fleet plan. The 319s are getting a little long in the tooth, but I flew a 319 and a 320 yesterday and the 320 was a pig and the 319 was a peach.
Another tidbit, a few years ago United was scrounging for second hand 319s and picked up a bunch from China. The Spirit 319s were also slated to head to United, but it never happened.