A Rainbow Dash vinyl collectible recently turned up on eBay. It was labeled a prototype, but appeared in-box. Her mane colors are a bit off, otherwise she looks to be well-made. A blank vinyl pony prototype also showed up on an online store called Gemini Collectibles, produced by Funko.
Not much more is known, but fingers crossed that these are legitimate!
Thanks to Equestria Daily for the information. You can see more pictures there.