Yes, the general concensus would be to avoid discussing the relationship at the moment. As you probably have seen, it tends to add pressue to the situation
There are no gurantees that your marriage can be salvaged, but do you understand why she is leaving? Knowing what has broken the marriage from your wife's perspective is going to give you clues as to what you might need to do if you dont want that to happen.
Typically, its not one or two things that compells someone to end a marriage. It tends to be a cumulation of unhappy experiences over time that someone gives up hope that the union will be fufilling & rewarding for them.
If you want to stop this from happening, you need to understand your wife's POV on the matter. So far, you have not mentioned anything as to why this is happening so its very difficult to give you any bit of useful info
Me: 37 Wife: 40 Son: 7yo Son: 18 mo Bomb: 12/31/07 Status: Reconciled 1/2009 but backsliding terribly right now