In one of his post-sacking, pre-hiring interviews, Jose Mourinho talked about how teams tend to plan pre-season well before it comes time for it, so any manager coming in to a new team only has limited control over the schedule. It would appear that Chelsea may go even beyond the usual one-year (?) planning period, at least when it comes to a trip down under.
Apparently, Chelsea will be heading back to Australia after the 2018 World Cup, at least for one match against Perth Glory FC in the 2018-19 preseason — probably more either in Australia or in the wider region, as in 2015, when Chelsea did a post-season tour of Thailand (Bangkok) and Sydney.
There's no exact date set for the fixture yet, but it will take place after the World Cup final and is the first booked event at the new Perth stadium. It may not be the first event held there, though Chelsea have recently made a habit of opening new stadiums. We were the first to play at Ferencváros's new digs in 2014 and have three more coming up this preseason.
I suspect the trip to the west coast of Australia won't be officially confirmed until roughly two years from now, but if you're in Perth, mark your calendars!