It is the mission of any good trust to fulfill the wishes of the grantor. The duty of the trustees is to fulfill the wishes of the grantor. However, of course, the general principle in life also applies to trusts, which is “you can only get out of it what you put into it”. So the idea of the grantor “always being taken care of” depends upon the trust having been given enough resources to make that possible.
Assuming, though, that the grantor has put adequate resources into the trust, and the trustees administer those assets properly for preservation and expansion, then yes, the grantor’s wishes can be fulfilled . . . even though the person who played the role of grantor in the beginning will have long since had that title expire. After the grantor position has been extinguished, the person who played that role will have some other role, such as one of the beneficiaries.
In cases where the original trust client elects to be one of the trustees, then a nominee grantor is selected to play the grantor role. In a setup like that, the original trust client, the one who becomes one of the trustees, is the one whose wishes must be followed in the administration of the trust.