Leona Lewis is definitely not a one-hit wonder. Seeing as how she recently released a single with a variety of artists that include Beyoncé, Mary J. Blige, Rihanna, Fergie, Sheryl Crow, Melissa Etheridge, Natasha Bedingfield, Miley Cyrus, Carrie Underwood, Keyshia Cole, LeAnn Rimes, Ashanti, Ciara & Mariah Carey in dedication to Cancer and her album was re-released back in April, it's hardly a one-hit wonder. It takes a while to produce a song and release it to the public. Just because she isn't exactly releasing new material, it doesn't mean she's going away into the dust. It means that the media isn't going to focus on her when they can focus on people who are in the middle of a tour, or recently released an album. It's as simple as that.
I've never been a fan of Alicia Keys, so I don't have anything to really say about her.
Colbie Caillet has an excuse to not be mentioned as much since she recently got engaged to her boyfriend.
So to answer your question, no I'm not. I get anxious when I know that they should be recording another song or album, for example - Ashley Tisdale (who's currently focusing on her own album now after completely the final installment of High School Musical). I was wondering for ages why she wasn't releasing at least a single as it's been about two years since she released her first album. But regardless, she was busy doing other things like filming and focusing on High School Musical.
The point is, in my personal opinion, there are few 'one-hit wonders' that I have in mind since the majority of them are often busy focusing on other parts of their life. They don't at all disappear unless you let information about them and what they are currently up to to disappear. It's really as simple as that.