The Legacy of the Beast tour for 2019 is pretty much confirmed. The biggest question is the timing: will they bring the show to Asia, Australia and possibly somewhere else in... let's say, February-March, have a little break and then do another leg in july-september, if they'll headline Rock in Rio. If not, summer tour similar to 2010 or 2012 is pretty likely. Closer to 2010, really, if they'll end up doing a couple of European dates in addition to America(s).
However it'll turn out, writing and recording a new album in late 2019 sounds like something they'd indeed do. After all, they had a lot of ideas in 2014 and Bruce said in his book that with a short Maiden England run during the summer, they were ready to focus on that new album. It would have been released much earlier in 2015 if things didn't turn out as they did. In the end, they DID turn out incredibly well, but my point is, that TBOS might have been out much earlier, had there not been a cancer. With that in mind, touring during next summer, writing and recording sessions late next year and an album release in early 2020 sounds very likely to me. Early 2020 would be tricky with tour dates though, assuming they'll tour that summer; tour announcement in late 2019 would give fans much more time to prepare. Can they get a new album out as early as late 2019? Perhaps. Will they? That's another question. It really comes down to what kind of plans they have next year: do they take some time for planning the next album early next year, or is late 2019 the earliest possible hour for them to give it a proper thought? Will TLOTB go for a third year? It might, but I think not. A live release around xmas 2019 would be interesting too. And then, album release next year. So many options...