I'm not expert on this issue however, I would assume the vBSEO links will become invalid and eventually dropped and the content rediscovered/updated on the new links. I've certainly seen invalid links on analytics which were eventually dropped
I think he's referring to links from other sites. If I'm linking to your site like this:
And your remove VBSEO, the thread URL will become something else. Don't want that to happen. Of course it all depends on how important his links are. I know I couldn't possibly lose mine, and that's the only reason I still run VBSEO.