While v5 looks a lot better with more features (bells and whistles). It's better to stick with what we have now. I guess all we want is a good forum that won't break.
The latest version still has a bit of issue with styling not working now and then. v4 is pretty much ironed out the problems but not worth the effort to upgrade. v5 is good for mobile thou.
I would say, wait until this one break or v5 is dead stable.