True. Though I was only basing this off of comparing to having Lady Gaga sing for Queen. If it were a decision between the two, I would've chosen Lambert over Gaga any day. There's probably a few vocalists that would fill Mercury's place very well, George Michael is definitely one of those people.
Perhaps Queen is just experimenting with vocalists at the moment to see if they can find that one vocalist that fits them well. I mean, first we hear about Gaga performing with them, now Adam Lambert.
If they end up having Bieber sing with them, all hope is lost