Oyster and world

My understanding of  "the world is [whoever's] oyster" is that the person has boundless opportunities, that is, that he/she can potentially do anything.  The saying doesn't specifically connote that this is a result of the person's skill versus fortunate circumstances; it could be for any reason.  I believe there is a connotation that what one can get out of this opportunity is either personal accomplishment (i.e. doing the things you want to do in life) or wealth.  I've always assumed (but have never heard explicitly) that the reason for "oyster" is two-fold: 1) oysters in many places are considered a delicacy, a somewhat decadent food item associated with the rich or aristocracy; 2) oysters are where pearls come from; thus, perhaps if "the world is your oyster," it means that you have the power to seek out your "pearl" whatever that may be.  For comparison, I think "the world is your oyster" is perhaps idiomatically most similar to "the sky's the limit" (assuming for the latter that you specify "for you").