I've made the jokes. We all have. I watch "Sesame Street" all the time now with my son, and there are many, many times in which the initial shot of the Ernie-and-Bert segment makes it look like they're in bed together. But no, they're not, in fact, gay, and regardless of whatever online petitions are out there, they're not going to get married.
Why can't a couple of Muppets just be heterosexual life partners for two or three decades? These people are living in a world in which "Avenue Q" doesn't exist.
And they're not named after "It's a Wonderful Life" characters, either.