P.12.1- All "at end of turn" abilities trigger and go on the stack, then the current player receives priority to play spells and abilities. [CompRules 1999/04/23]
P.12.2- Any new "at end of turn" abilities that trigger during this step wait until this step in the next turn. They are not played this turn. [D'Angelo 1999/05/01] This means you cannot get any loops using "at end of turn" effects.
Note- "until end of turn" effects do not end during this step as Rule P.3.4 might indicate. They end during the Cleanup step. See Rule P.13.1.
Note- Unless something happens during the Cleanup step to give a player priority, this is the last step in which players can use instant spells and abilities before the next turn's upkeep step. [D'Angelo 1999/05/01]