I think they put out a retire on 2.5. I think that the existing rules will work, but you can't edit them or create new. I could be wrong, but I remember people encouraging migrating to RM4
Actually, you're wrong. You can continue to use and edit your 2.5 Rules to your heart's content for as long as you want. You cannot create new ones but existing rules can still be used and edited just fine. I still have a few that I have had absolutely no reason to re-write since they are working perfectly and I do not need any of the new features in RM 4.0. In fact, they are some of my fastest running rules, not being weighed down by Global Variables and whatnot. If you want a blast from the past...