OK, by putting 2 and 2 together, I'm pretty confident that this will be a collection of dinosaur bones added to the MakerBot Digital Store.
If you visit the digital store (digitalstore.makerbot.com), you will see this image on the page:


The dinosaur is identical to the one in the last MakerBot tweet


The questions that remain are:
When?
How Many Dinosaurs?
How much money?