Those Cthulhu decks were available back in January.
Yeah, but I just received my pledge yesterday! Still waiting on The Writhing Dark.
For a release to be a 2015 release, it has to be either:
1) available at retail for order (NOT pre-order) and in stock, or
2) in the hands of the Kickstarter backers, not merely in transit or waiting at the factory or wherever.
It's not uncommon for a KS deck to appear at retail first, because when ordering in volume, USPC will make free drop shipments to retailers who've placed large-enough orders for your print run. This makes way too much sense financially to pass up, despite how it can leave backers feeling disgruntled, especially if the creator is slow to ship. It would be silly and foolish to have them all shipped to you if you have to ship out a large amount of them to a few retailers elsewhere when someone's willing to do it for you for FREE. So it's possible these were out for months and are only now arriving in backers' hands - either way, it's a 2015 release (as long as they weren't for sale in December of last year)!