I ordered a Dark Angel Primaris Upgrade sprue on Saturday, along with a couple of other items, and I have just received notification from GW Customer Services that the sprue is out of stock and has been discontinued - as a result I've been refunded.
I've just replied asking for more clarification, as I'm guessing they're repackaging them in packs of two similar to the newer upgrades (Imperial Fists, Raven Guard, etc). If that is the case, then I'm guessing the Blood Angels, Ultramarines and Space Wolf sprues will be undergoing a similar effort.
The site doesn't show this at the moment, so I will keep my eyes open. If I get any more info I'll share it here.