Both the Kickstarter Campaign and the Summer Sale have concluded. The backers options have closed. Only previous Kickstarter backers may upgrade at this time. There are plans for sales that would include cosmetics and keys to Alpha / Beta sometime after PAX in Sept. All "exclusives" to the backers options will not again be available.Hope that helps
I think they mentioned being able to buy access to the various stages of testing. That being said. The unique awards from KS/SB are unattainable if you didn't back in time. I'm sorry.