You guys are kidding yourself and make me laugh
There will definitely be a European tour after the American tour. No need to announce it yet since the American tour goes well into 2019. There will also be an Australian tour.
After all this drama and "new band" they will definitely have a very long world tour. Its my opinion its probably the last gasp of Fleetwood Mac.
To answer the original question, the next leg will be announced spring 2019.