You hope that they won't be deleted but there's really no guarantee. I've been a CS user for some time now, but feel the product has become too expensive for the value I get out of it, so I'll just stick with an older version and be done with it.
Um, ok, fine, Dropbox could also delete your files. OSX could. Windows could. At some point, I guess you can't trust anyone, right? Point is - if you believe we (I work for Adobe) are lying about not deleting your files stored in CC, then just don't save them there. Or do what I do with Dropbox - I keep another copy on an external drive "just in case".
There is hardly a thing in the world that some man can not make a little worse and sell a little cheaper.