Brogan, if the vb 4 isn't using a blog or cms it can use the built in importer. I imported my vb 4.0.8 forum night before last without the 4.0 addon. But mine was a suite NOT using either the blog or cms or social groups, etc. It was a plain forum.Not yet.
I'm waiting for one myself.
Currently only a vB 3.7/8 importer (official) exists, and a vB 4.0 importer written by a member.