Rule 807.4j

If an effect would cause a player to take an extra turn after the current turn, but that player wouldn’t have a turn marker at the start of that turn, that player will take the extra turn immediately before their next turn instead. Example: During Alex’s turn, he casts Time Walk, which causes him to take an extra turn after this one. During the same turn, the player to Alex’s left leaves the game, which causes the number of turn markers to be reduced. After Alex’s current turn ends, his turn marker is removed. He won’t take the extra turn from Time Walk until just before his normal turn the next time he receives a turn marker.