From Fortnite Intel: “The in-game MOTD has updated to feature the Guided Missile under the heading Coming soon. With Content Update v5.10 dropping tomorrow, were very likely to see the weapon included in the patch. As described in the recent Dev Update as well as the description, the Guided Missile has been reworked and balanced to be used…”
Source: N4G PC Fortnite Guided Missile returns tomorrow