Creation kit had nothing to do with Skyrim's end game sales numbers. Only 14pct of sales were PC and they hit 7million units in sales just the first week of launch...
http://steamspy.com/app/72850
According to the last Bethesda spot about, Skyrim sold about 16M in total, since then (2012) no other ads and that's the retail, even the 14% was refered to the retail.
What made the sales of Skyrim? High impact and financial marketing first, Oblivion, his predecessor was the first open world arpg for consoles, so; but that as other say isn't a good quality indicator, before Oblivion there was the Gothic saga, a really good open world arpg that sold really low compared to the Bethesda franchise, and the response of why still the same, marketing, but in the opposite sense for this case since the PC game world affair wasn't curated and funded as the console business, since now..
The only way to ensure a good launch profit was a great media coverage, on the paper mostly, but times are changed, advertising, events, metacritic and similars evolved the procedures, even some developers signed some metrical terms for their profit under a publisher (Obsidian for Fallout New Vegas for example); all this "bla bla bla" to say that if a journalist tomorrow publish that with the RedKit you will make a miracle the game will sell a lot in a short time, I'm sure of that, if he say it's a mess the game will sell maybe less in a long term, that's the beauty of the modern marketing promotions.
Take everything as a personal opinion, but think just about the modgate for Skyrim, think about how much Bethesda could hearn for a single mod by justifying that in a tool release (nerfed tool that need third party software for a lot of modding production), and believe me they are diabolic in their marketing section just to think something of that or in such long term high profits,if the modding reaction/production since the release wasn't so high they wouldn't ever risk so much for an entire piece of market.
Well now sorry for the off topic.