It not just about making it before the tour - there is probably some pre-production and rehearsals that need to be attended. But given Mike's OCD, he'll figure something out.
Remember, Mike is famous for having an incredible memory and not needing to practice the songs. Neal Morse joked that he, and the rest of the band, would practice their parts for weeks before a tour - and Mike would come in and say he hasn't even listed to the material. It's apparently all in his mind and he can nail it from memory. Pretty incredible actually..
I think he remembers general grooves and song structures, but his fills might be a little bit difference. I remember in the documentary for the Whirld Tour, just before the show they would record at Shepherd's Bush for the official live album, he had to listen to the album version of "The Whirlwind" to get some fills right for the recorded show because he wanted them to be just right. I'm not sure about DT music he played live, but considering he lived and breathed DT for over two decades, I think he didn't NEED to try and re-learn all of those specific fills.
For something like Transatlantic that only tours once every 6-8 years, he probably needs a refresher on some of the more particular parts. He may have "The Whirlwind" down by now, but I'm sure learning all of
The Absolute Universe might be a bit of a slog, especially if they do the 98-minute Ultimate version.
-Marc.