I love them just as they are. I don't want to kick up any ~asexual wank by saying this, but since Sheldon is an actual self identified asexual and not just some bro that fandom people are attributing ~asexuality~ to, I'd be sad to see the writers feel the need to give him a straight relationship. I have an Amy and Sheldon relationship with a guy right now and I'm so happy, I wouldn't give it up for anything.