(Ed. note: much of this article applies for Xmas 2014 - start at the 3rd paragrah "In addition...")
Amazon and eBay Sellers:
Every year I give the same general advice for sellers when they ask "What toys can I sell this Christmas for big profits?"
For 2013, there's a good indication that Barbie and Polly Pocket won't have anywhere near the clout they had several years ago (so avoid that merchandise). Mattel (the manufacturer of those lines) is saying their strengths are in Monster High, American Girl, and Disney Princess lines (among others) instead.
In addition, I advise: avoid 'what's gonna be the hottest toy(s)' fads and predictions and, instead, buy (now and in the Fall) 70%-or-more-discounted sale/clearance toys of popular brands (Nerf, Disney, Legos, Marvel/DC, Hot Wheels, and dozens more) and popular characters (Ariel, Woody, Batman, Hello Kitty, Cars, Superman, Winnie the Pooh, South Park, etc. more). As Christmas gets very close, you can sell those-once-discounted items for full retail price or higher.
With Barbie and Polly Pocket, I am sure there are some exceptions to this downward trend. But in general stick to the clearly popular merchandise as mentioned above. And DON'T try to predict the 'hot new' toy (I did that and it's like playing the lottery- too slim to win).