I don't think keeping Guentzel and adding would have changed things for the Penguins. While the Wings have been terrible... 7 losses in a row and 3-7 over the last 10, Penguins have been 3-6-1 and equally terrible, hardly getting any production from their core. I think it's clear that the group there is done now, and it just comes down to how to dismantle things, without disrespecting what Crosby has achieved there.
Sadly, and maybe in some parts wrongly, what happens next is dependent on what Crosby wants to do. Is he willing to participate in a full on rebuild, will he move to another team?
If I look at their current roster, there isn't a single untouchable there to me.... basically move anyone, and everyone, that you can get some value for. I know the hate for Dubas, but really some of the contracts signed by Hextall are so bad, that the org is in such terrible shape, with little room to move, not to mention the worst prospect pool in the league.
I mean Letang is signed until he is 41, Malkin 39, Rust 35 (four more years).. it's just terrible.
But you've really just got to move everything that isn't nailed down.