I think the future is bright for such bands. Given that the original musicians are dying out but the legacy stays. I don't want to campare Bon Jovi to Beethoven but you know, that kind of music lives because there are people performing it. One day it could be a similar case with rock music.

I love a Czech Queen cover band because they are musically and vocally perfect. What they do is called concert theatre. They dress like the band and perform to evoke the feeling of the original band, they say they play the characters. It's actually the only thing I don't like about them. I go to their shows because the singer can nail Freddie's vocals and overall they sound excellent not because stupid wigs.
On the other hand - Queen's music is so legendary that it might be reaching Beethoven's status. Even Queen themselves produced a live show called Queen Extravaganza. Meat Loaf is planning something similar. It aims to the concept that TSO do - the singers and all band members are replacable.

Sorry, all the BJ cover bands shared recently suck. I love Bounce because they have found the right way to do it. They are themselves, even though they incorporate a few typical BJ things, moves or the guitars etc. However they play the music and it's about the music. They do rarities and even they played three shows with an orchestra and many of the songs were totally reworked.