it looks like they are just hanging in there ... they let these bull runs happen at the weekends to relieve some pressure when new fiat cannot get into the exchanges to send it rocketing, then save up their dumpage for a monday-tuesday dumpathon ... but it's all looking quite desperate, at some point they will run out of idiots to borrow coins from and then the market can find the monetary premium instead of bouncing along on the cost-of-production floor (which is ever-increasing and soon to be doubling anyway)
I don't think its leveraged coins being dumped, But I do think when the tide turns it's fiat from these dumps (and a touch of FoMO) that are going to push bitcoin higher than it's ever gone before. Gmax panic attack yesterday gave some new hope to Core increasing the on chain block limit.
edit: there is also a lot of dark pool trading happening in bitcoin that's a big lot of coin that isn't hitting exchanges, I'd guess it's largely responsible for the long period of price stability. I'm also guessing those off exchange block trades are drying up now as some early adopters are running low on coin.