Talking to MTV, Harrison Ford claims that he is still not involved with Star Wars: Episode VII and that he won't be returning as Han Solo, even though he is. Basically, he can't talk about it until an announcement is made (probably at Disney's D23 Expo later this year).
When asked if it would be difficult to return to the character, Harrison Ford had this to say,
"Are you talking to me? Are you talking to me? I'm not ready at this time to have an in-depth conversation about...What did you call it again? Star Wars? No, can't talk about it."
"I think he's a great story teller. He's developed an enormous filmmaking skill. I think it's a daunting project, and he's the type of guy that can take on huge challenges and live with it. He is an awfully nice guy. Wonderful guy. Very happy he is involved with the movie. Even if I'm not."