The Futon Critic lists 508 and 509 airing as the 2 hours for 11/15, so it’s definitely not 508 being extended into 2 hours itself:
http://www.thefutoncritic.com/showatch/once-upon-a-time/listings/
[adrotate group="5"]
ONCE - Once Upon a Time podcast
Reviews, theories, and talk about ABC's Once Upon a Time TV show
The Futon Critic lists 508 and 509 airing as the 2 hours for 11/15, so it’s definitely not 508 being extended into 2 hours itself:
http://www.thefutoncritic.com/showatch/once-upon-a-time/listings/