I would do that trade. Crosby isn't going to keep up a 160 point pace, and in fact, if Richards gets traded out of Dallas, expect Eriksson to fall off his pace significantly as well (which he will do anyways). It's a good deal for you, you're going to get 4 guys who are guaranteed to perform, and giving up 3 guys in the deal who may not (Eriksson, Bob and Krejci).
Although if you can, I'd find a way to try to keep Crosby.
I could see why trading Crosby would scare people away, and I agree with the guy who said if you can find a way to keep him and do the deal you should, but it's still a pretty good deal anyway. Like everyone already said, with the exception of Crosby you're trading some not-so-sure things for 4 definitely great players. Seems like you'll benefit greatly at pretty much every position without losing much except for Cindy.