I understand this line of thinking mostly because it's very commonplace, but I do think it's a losing formula. This suggestion of "just get into the playoffs and see what happens" is a nice little sales pitch but it's mostly ********. We all know that.
The cutthroat decision that can set you up to really compete is being willing to cut bait. By any reasonable standard this defense is bad to mediocre, and bad to mediocre defenses don't win Cups. So either you get this defense to another level before the deadline, or "see what happens in the playoffs" is basically "sell a round, maybe two of tickets and lie about our chances".
So unless Sweeney finds a way to add a real top-pairing defenseman without stripping the forward group, I'd like to think he'd be willing to move Loui, Chara or anyone else in an effort to build a roster in 1+ seasons that doesn't have any glaring holes. I hate the idea of "Sinden playoff-banner" management, keeping their fingers crossed that a draft pick pans out at some point. It's just robbing fans.