There have been multiple Disco Rooms spotted in various places across the map in Fortnite since the V.3.5.0 release earlier today. The recent #BoogieDown contest may be the inspiration for these added rooms:
Looks like some data mining has revealed that these rooms will be featured in next weeks (week 90 challenges:
DISCLAIMER: As always, challenges can be changed at any time and may not be in the week 9 challenges.