[Nikolaj]

Well, even if Rod Stewart and Stevie Nicks tour together, Dave Stewart could be in Stevie's band, perhaps even as 'musical director', or as a bandmember. It is likely Dave who best knows the new material he produced for SN, so for the 3, 4, or however many new songs she plans on having in her set, it would make sense for him to be in the band.
If not as her musical director, should that go to Waddy, Dave Stewart could still be on board.
Eons ago, she had Michael E, then quite young, as her musical director for a tour, so you never know-she could do the same with Dave Stewart, even if she tours with Rod Stewart. Stevie may be touring with two Stewarts!
Or, add Sandy Stewart on backup vocals, and it could be three Stewarts with her! Or no Stewarts!