Bert and Ernie, who've been on Sesame Street for 25 years, do not portray a gay couple, and there are no plans for them to do so in the future. They are puppets, not humans. Like all the Muppets created for Sesame Street, they were designed to help educate preschoolers. Bert and Ernie are characters who help demonstrate to children that despite their differences, they can be good friends.
When I denied the "gay couple" rumor, my friend asked: "Well, what about that Muppet with HIV?" She was worried about her daughter growing up too fast, and said there were some things kids that age shouldn't see on TV. I explained that Kami was meant only for the South African production of Sesame Street, where some younger children were born with HIV--and that there were no plans to include that character in the American version. (If some new Muppet character were created to represent a major problem that affected mostly American preschoolers, you wouldn't expect to see that Muppet in a foreign production...especially not if people in the other country associated that same problem with homosexuality and drug addiction!)