I think there is a world in which the Cubs can trade Stroman and still make the playoffs. Can they trade them both and still make it? That is extremely unlikely.
With that said, if that hypothetical scenario occurs where the Cubs trade Stroman and do make the playoffs, then the deal almost looks worse.
On one hand - Yay, we got something for Stroman and still made the playoffs!
On the other hand - We made the playoffs, but now don't have our best pitcher in a short series, so what exactly are we trying to do here?