I think the singer has already been chosen and this is just a way to hype the band. Remember there is a story they were already searching for a singer before they announced chester was leaving.
If they already found a singer, they would be hyping the band by announcing that singer, not by doing an internet search. They are clearly itching to record and perform again, there is absolutely no reason they would have found the perfect candidate already, but decided NOT to record with him so they could spend a few months sifting through fan recordings.
They'd get more press announcing that new singer than by doing this, anyway.
I think they just haven't found the right guy through their auditions, and rather than settling for someone they don't feel 100% about or giving up, they are throwing a hail mary and seeing if the right guy is online.