I hate to not actually "answer" a question, but...anyway.
I don't think they would stop ribbons, there is no reason to. After all, even HG and SS have ribbons, and they don't even have Contests- the main source of ribbons. Besides, if Pokemon can migrate from Gen.4 to B/W they'll be holding any ribbons. Another reason to keep it going. Ribbons tell a story! I don't think they would get rid of that. Do you?