finally got the deck migration running - when you start forge, if there's a all-decks2 file, you're asked if you want to import it. this version has all the decks already imported, and the all-decks2 property commented out, so you're not asked again.

src/Deck.java

@@ -1,13 +1,12 @@
-import java.io.Serializable;
-import java.util.ArrayList;
-
-
 /**
  * Deck.java
  * 
  * Created on 26.10.2009
  */
 
+import java.io.Serializable;
+import java.util.ArrayList;
+
 
 /**
  * The class Deck. This class is only here for compatibility with forge versions 10/17 and older. When it is read
@@ -25,7 +24,7 @@ public class Deck implements Serializable {
     private boolean           isSealed;
     private boolean           isDraft;
     */
-    
+
     private ArrayList<String> main;
     private ArrayList<String> sideboard;