I was talking with DH about this last night. We could see Virgin picking up HAL... their current line is no kids but sways young adult (I'd guess 25-34/ 25-49) If they could keep enough of the HAL vibe, they could appeal to the slightly older demo of HAL and expand their "empire".
Whatever may happen, I will be very sad if we lost the Holland American Line experience. It may not be what it once was, but it's better than if it were gone completely.