As long as the lead singer is still there, I don't think anything will change very much.
It sounds horrible, but this band has popped out of nowhere and I'm still unsure if I enjoy their music. I mean, they have a nice tune every now and then and the albums hit the nail right on the head in terms of the music I usually like, but to me this isn't much of a blow, and the band will soldier on in the same vein that they usually do.
Am I missing something?
While their definitely isn't complex by any means, Marcus is a really solid drummer and a pretty big part of their live show. Not that another drummer couldn't be as well, I just really like his playing. I am curious if they'll replace Delia with a new keyboard player or just drop that element entirely since they have a second guitarist now.