I'm having a hard time deciding on bedding for our registry. Right now we share a full size bed, which is pretty worn and I would really like to replace it in the near future, as well as probably go up to a queen. But in reality I don't know how soon that is going to be. I'd like to register for a nice set of sheets, as well as a duvet cover, etc., but don't know if I should register for sheets in the size of bed we have now or with the future in mind. Should I register for the bigger sheets, in the hopes of getting the new mattress? Or should I stick with the size that we have now?