If Tours in DHS were going to be rethemed, then Disney needs to start working on a new film, matching jostling algorithm, and a plan for the queue and store, complete with fabricating all the props and scenery. And they need to start working on that... now.
But, no insider has said they are. Just that the 'plan' is to retheme it 'after' SWL opens. So, if SWL opens and management says, "OK, what shall we do with Tours?", well, then don't expect the retheming until 2020, or 2021, or 2022. That's if they they have the heart to take it off line during the huge crush of people visiting the park for SWL and there's a line just to get into the land.
The only thing that I can think would make it likely for Tours to be rethemed or go away is if in the next year or two someone at WDW wants a new Land taking over Indy and surroundings.
Though, for all I know, they already have secretly started on a Muppets retheme that will be ready to go lickety-split at the end of 2019.