The best substance I have found so far to assume that there would be a tour next year are the statements by Trooper VIP staff that events are scheduled for next year. It sounds likely to me that this could be a source of a leak. So that leads me to speculate about what a tour could look like.
Bruce has made it very clear in his onstage rants this year that whatever will happen, it would not be another Book of Souls leg. Of course, onstage rants are always to be taken with a grain of salt, but he said the same thing on every gig, and I remember how he started talking about pyramids in the 2007 shows. The persisting rumour is that it would be a Legacy of the Beast themed tour. I'm not going to deny that possibility, but based on the observation of the last ten years, I'm a bit skeptical. Ever since 2006/2007, there has not been a one-off theme for a tour. Every theme was used for at least two years, despite setlist changes and venue type (indoor/outdoor/festival). So whatever the stage design, for instance, if we see it in 2018, chances are high that it will be carried over to 2019. It's just the economy of their touring these days. I don't think Legacy of the Beast would sustain that sort of tour, it's already a year old and it would make no sense to promote a video game from 2016 in 2019. Or even 2018, for that matter.
There's also most likely not going to be another history tour in the sense of The Early Days, Somewhere Back in Time and Maiden England. The most logical next step would be to release Live at Donington as a DVD, perhaps with the History section covering the whole nineties, but I doubt it would become the base of a tour. I would love to see it, but there's just not enough commercial appeal from a strict business viewpoint, no matter what the chart positions in the early nineties were. Kids today don't remember Tailgunner or From Here to Eternity, and Iron Maiden inc. won't risk it.
I could see another TFF scenario, though. Maiden might record a new album for a September/October 2018 release and do a summer tour the way they did in 2003 and 2010. Maybe, just maybe, this would use some sort of Legacy of the Beast theme, but I doubt it. They might plug it somewhere, like they plugged the Trooper beers. Now, one can dream and hope Maiden would be as bold as they were in 2010 and play a nineties set for the summer tour. There are a few songs I could see them doing: Afraid to Shoot Strangers, Bring Your Daughter... ... to the Slaughter, Sign of the Cross, The Clansman, Lord of the Flies, Man on the Edge and Futureal, as all these have been played since 1999; Tailgunner would be another good bet, and Bruce once did a one-off performance of Be Quick or be Dead somewhere (I think
@Forostar posted a video of that), so that's another possibility. That's already nine songs, so that may leave room for one or two deep cuts or just a few more classics.
So that's what I would speculate on based on observation, but Maiden have surprised me often enough in the past, and I'm not going expect anything. They might, indeed, do something unique or surprising - who knows?