They don't need a patent to keep it private. Just make sure no plant material gets out of your hands and you can keep a variety private forever.

If you're interested, here's a good article about them. Based on this article it doesn't seem like plants will be for sale anytime soon. We bought a bag last week and they are really good. Not $6 a bag good, but good. I didn't find them to taste much like cotton candy, aside from both being sweet. I won't begrudge them for the marketing ploy though. I don't normally like white/green grapes but these were good. That being said I regularly get red/black table grapes from the supermarket that were just as sweet.

Here is a link that might be useful: Cotton Candy Grapes

I dont think you can patent a fruit. Its obviously a graft of seedless varieties.. I mean they dont have to tell the technique or combination if they dont want to but they cant stop anyone who figures it out from applying it.

It's a hybrid of a concord type grape and Vitis vineferia, a common grape and yes, it is patented. It takes thousands of tries with no guarantee of success to breed these designer plants. Cotton candy grapes