In a surprising turn of events, American Girl said this on Facebook about Molly's return:

"A special Molly collection is being exclusively sold in limited quantities and in limited Costco stores. While we’ve offered exclusive items to our retail partners in the past, it’s always possible we may bring Molly back into the American Girl fold but there are no plans to do so at the current time."

I think American Girl planned to bring Molly back in full-scale, but after seeing how poor Felicity and her limited collection did, they just sold the stuff they had at Costco. What do you think?