From www.wdwinfo.com

Standby line to be cut off in Anna and Elsa meet and greet
Jul 23, 2014

In an attempt to lessen the lines of guests waiting to meet Anna and Elsa, Walt Disney World is testing a timed return ticket program, which sounds very similar to the original FastPass system. Guests who do not hold FastPass+ reservations will receive a ticket, giving them a specific return time and stating that "there will be a moderate wait" when they return to the line. Guests who are there first thing in the morning will still be able to enter the standby line, but cast members will cut the line off to standby guests once it reaches the building's entrance.

This system will be tested for a few days to determine if this will help with the wait times. Lines to meet the Frozen princesses are often in excess of 300 minutes.