Another thought about trading Hornqvist: where are you going to play everyone? Right now, the Penguins have Guentzel, Hagelin and Kuhnhackl on LW, Sprong, Kessel, Hornqvist and Reaves on RW and Sheary, Simon and Rust that can play both wings. The biggest problem I see with trading Hornqvist is that I struggle to come up with a wing group that I like, since the Penguins would have so many small skilled wingers. You'd probably have to trade both Sheary and Hornqvist to get a 3C and LW (speaking purely from a roster POV), since I don't think you can do less than that. I'm struggling with coming up with the rest of the roster, that's my big concern.
If you trade Hornqvist, that makes it Crosby-Sprong, Malkin-Rust and 3C-Kessel as the C-RW duos. How are you going to fill out the rest of that? Is Simon an everyday player in your eyes? He's not in mine, he should be viewed similarly to Sheary in 2015 as far as I'm concerned. If you have Simon in as an everyday player with Crosby, I'm not sure you need a winger for Malkin anymore, because your 2nd line would be Guentzel-Malkin-Rust. You need a LWer for your 3C and Kessel at that point. If Simon isn't an everyday player, you either need to keep Sheary (so probably Sheary-Crosby-Sprong) and you only need a LWer for your 3rd line, or you trade Sheary and you need a LWer for both Malkin and the 3rd line. But in this case, you don't need a physical LWer for Malkin, you probably need more of a skill guy.
If Sprong sticks with Crosby, I think the best bet is having Guentzel-Malkin-Rust as your 2nd line. It works well and you can still run with either Simon or Sheary with Crosby and Hornqvist. At that point, you just need to work with the 3rd line. You either need to do that or drop the idea of having Kessel and Malkin on separate lines.