Scottish midfielder will have another loan spell away from Chelsea and will leave to another club this summer.
The youngster has been released from the club’s first-team pre-season tour of the United States.
Gilmour is set to join up with the development squad instead, along with Armando Broja, Harvey Vale and Tino Anjorin.
All three players are likely to be loaned out to clubs in the Premier League or Championship in the coming weeks.
Gilmour was very impressive at Chelsea under Frank Lampard, but struggled under Thomas Tuchel and did not have a good loan spell at Norwich City.
He will now be hoping to get a loan move to resurrect his fledgling career.
Lampard is now in charge of Everton and could look for a reunion with Gilmour at Goodison Park.