The last ability of Growing Rites of Itlimoc doesn't trigger if you don't control four or more creatures as your end step begins. If you don't control four or more creatures as it resolves, it does nothing.
If you control a creature that will be removed from the battlefield "at the beginning of the next end step," you can resolve the ability of Growing Rites of Itlimoc before that creature leaves the battlefield.
If you gain control of a creature "until end of turn," or if a noncreature permanent you control becomes a creature "until end of turn," it'll be a creature under your control through the entire end step.
For more information on double-faced cards, see the Ixalan mechanics article (http://magic.wizards.com/en/articles/archive/feature/ixalan-mechanics).