I really think you should move to the new forum but retain all posts, etc.

The only thing I believe would be a plus is to purge the members list of anyone who has not been active for 1 year of more. I'm sure you have many members shown who no longer have an interest in the site or possibly never had a real interest to begin with. When these people are left on the list and never active/no posts, etc. it just takes away the benefits and value from the rest of us. Is there any specific reason why those names should remain as members?
I went through the list the other day and could not believe the number that have never had a post!!