As for the helping people with suggestions of unreleased stuff, agreed, people should try to help others with current available elements and if possible/known with stuff the guy actually has, it hasn't to be perfect it's also a game of making due with the means at hand.
As for spoiling stuff, I think most of the times it becomes clear rather fast if someone is talking about new or current stuff, and depending on your position you can read on or not. At least for my own preference this is enough, since one can get a rough outline of the expansions without spoiling oneself with all the details. Sure, a bit more indication in thread titles wouldn't hurt, but that is a generic forum problem.