I'm going to the London show on this tour next Thursday, but to be honest, I'm probably going to watch Evergrey then go home. I've no real interest in seeing Kamelot with a guest singer when I've already seen them three times with Kahn, and especially when that guest singer is Fabio Lione.
Maybe if they get a killer permanent replacement (which will probably be Ripper Owens), I'll be interested in seeing them again.
If I were to be brutally honest, they may never recover from this. They already had to downgrade a bunch of the venues on this tour, including in London, when it was announced Kahn wouldn't be touring. Now without him, I don't see their popularity continuing to rise like it was before.