Find Your Cruise
I guess its not impossible that you could be upgraded to a higher grade inside cabin or even an outside cabin, its never happened to me but you never know it depends how fully booked your cruise is - have you had a look.
About the same as winning the lotter.
No, its never happened to us either, in 15 cruises with a number of different cruise lines!!!But dont give up hope, miracles(may!) still happen.