My .02
I think rotating setlists, particularly since DT has a lot of songs, and a lot of LONG songs, is very much the right way to go. Also, in the internet age, setlists are often spoiled very quickly. Rotating keeps things fresh for the band, fresh for people who are able to see multiple shows, and keeps things a little bit of a surprise even for people that keep track of what is being played each night. All in all, I find it to be a very smart move and hope DT does indeed do it again.
If DT typically plays 15 songs in a headline set, then learn 30. And choose what to play the morning of the show, and use soundcheck to refresh. For musicians of DT's caliber, that's not really a big ask. And I would think fans would really appreciate the band's willingness to do so.
My favorite current band, Alter Bridge, swapped a few songs in and out of their set over the last tour and it was very much appreciated. I miss the times DT was doing that. I'd welcome a return to them.