I'll probably have a hard time getting behind any unknown singer, but regardless I actually think the best move for STP would be to time the announcement with the release of new music, similar to what they did with Chester. Basically it says "we have this guy and this is what he can do... we're moving forward". In my opinion, thats the best way to make a real go of continuing their career. If you announce a replacement singer and then just play the existing catalog, then you're probably not far off from becoming a state fair band.
I think it was clear from the beginning of the auditions that they will be writing and recording new material with the singer they will choose. The real question is what kind of musical direction they will take, aside from the ability of the new singer to do the catalog.
Mickey Valentine stated one time on Facebook that the new material will be a little resemblant to No4 and Shangrila Dee Da.