Seems like little more than a clever way for them to dump their massive holdings. The question I'd be asking is, why are they exiting Bitcoin? Maybe they see the writing on the wall?
Your thinking very short term here, the people that get involved with things like this (i.e. the winkelvii) aren't looking to exit a possible 100 billion or trillion usd venture for a mere 1000% ROI.
bitcoin is the first p2p digital currency (that I know of) that has gained this much traction and attention capable of possibly disrupting the worlds financial industry and breaking the monopoly of the fed and other world banks.
People like the winklevii don't lose, even when they lose they win, i.e. the facebook lawsuit.
That's only if you believe in the delusion that you've laid out. "possible 100 billion or trillion..." This will never happen with Bitcoin and while I don't presume the twins are the sharpest tools in the shed (i.e. getting jacked for Facebook) they are certainly far from stupid. Bitcoin peaked in media attention over the last couple of months and mass adoption is virtually nill. No amazon, ebay, Paypal or any other major company accepted Bitcoin. Not because they don't know about it but purely because they are not interested in dealing with Bitcoin.
Now, nobody knows for sure what the twins are up to but they certainly can't just dump their holdings on the open market and this seems the mostly like way to accomplish that, while reaping a massive profit. My gut says this is an exit strategy because the "traction" you speak of, does not exist. Time will tell.