Guess who’s rounding out the final season of “The Oprah Show”? It’s none other than D.C.’s own sisters of sweets, Sophie LaMontagne and Katherine Kallinis of Georgetown Cupcake. We know how much Oprah loves cupcakes, and now the daytime talk show queen is sharing the scrumptious confections with the entire television audience. Which flavor will they serve? Sophie and Katherine, who also star in TLC’s “DC Cupcakes,” said on the Tommy McFly show: “Everything we heard about her was true. She’s very gracious, down to earth, so funny. …” The little bakery has surely received a good amount of notoriety this year and has contributed to the cupcake craze around the country. Their “Oprah” show will air at 4 p.m. Tuesday.