According to what daughter Liv Tyler said on Jimmy Kimmel Live, it looks like he might be.

It would appear that he is working on a solo project, or, he's at least come up with a few new songs on his own.

This came to light when his daughter, actress Liv Tyler, let slip the following when interviewed on Jimmy Kimmel Live:

Whether this affects  plans for a new Aerosmith album remains to be seen.  Either way, the man is certainly staying busy.  I'm sure Aerosmith fans were relieved to hear Liv say that was was recording with Aerosmith.  He's doing American Idol, we've seen him in the studio with Aerosmith, and now he has this possible new solo project.  Love him or hate him, you have to admit, the man is machine when it comes to his career.