From Tidbits January 2018:

Quote Originally Posted by INTERCOT Tidbits

A Little Less Mania

1/21/18 Toy Story Mania has begun work to re-route the attraction to be entered and exited from inside the soon-to-open Toy Story Land. For the coming weeks, Guests may notice longer than recent wait times as phased closures occur on the third track followed by the two original tracks. After the phased closures, a full attraction closure is expected to complete the project closer to the Summer 2018 opening of the new land.
In addition to the extended wait times due to partitioned refurbishments, Studios Cast have now reported a temporary suspension of FastPass+ for the popular attraction. FastPass+ has been reportedly suspended from April 9th through May 7th, 2018.

The omission of this attraction from FastPass+ selections is also expected to put heavier demand on the other attractions in the same tier during this period.