Any particular reason you want to avoid upgrading?
because 4.0 is a completely broken piece of garbage?
I'd say until there is a solid reason to convert over to SM4, just stick with 3.9. 3.9 is fairly reliable, has support for everything except freeze rolls (and if anyone wants to use those they can use the SMO build), and is already in use by most people
I don't see any reason to upgrade to 4.0 right now, nor do I really see a reason to make a theme for it