Yes, in the end either Apple will draw users into its "ecosystem" via iCloud, or it will remain a handy option for Mac-only users. Dropbox has filled a need for me (synching across multiple Apple devices) that Apple could easily expand to new areas by leverage the native OS.

Then it becomes an issue of trust – who is putting more skin in the game to protect my assets? Dropbox has always had a problem establishing trust for users like me who absolutely cannot afford any negligent gaffes like leaving my account open to accept any password for a few hours. On the other hand, Apple has a very short track-record as a manager of a big, shared data repository open to the general public.