I think in Slash's autobiagraphy he mentions they interviewed Sebastian Bach the first time around and that he didn't work out. Afterwards Bach appearantly had a bunch of bad remarks to make about the guys in the band...I think it would be cool if he got the gig though.
Cornell blew his voice out a few years ago. I have spoken with studio engineers who have worked with him over the yars, and they say the difference between Cornell (Soundgarden) and Cornell (now) is mind-blowing, and sad.
Perhaps its time for another edition of 'Rock Star' where they audtion lead singers ala 'American Idol'? Slash could screen the perspective vocalists while using his 'Guitar Hero' kit! ha
I fear that Audioslave, who I thought was fantastic, will make more bands and singers think they can have success a second time around again. It's worked in the past, but seems to be an epic fail for most these days.