whether you pledge the KS campaign for a digital tier or you buy the SEA, the situation is exactly the same. If you want the digital content : upgrade your version If you want the goodies : buy the CE, you can still sell your 2 steam keys then...
And as said before, Kickstarter and SEA gave you the opportunity to pay the game at a lower price than the release price AND you could play to the alpha and beta version giving your advices and feedbacks