That F9 would eventually add Jacksonville (or thereabouts) is not entirely surprising, but I could think of the locations that likely would have been ahead of that in terms of attractiveness - MYR, PBI, even Nassau, Bahamas.
The other thing I am wondering about is if this means a new Indigo strategy away from primary airports - would they switch services, for example, from Fort Myers to Punta Gorda, from Orlando to Sanford, and from Tampa to Clearwater.
Also, down the road, is this an indication that they will go into places like GYY (and exit MDW) as well as BED or ISP (which may lose its WN service after 15 years).