g1smd - 11:09 pm on Jul 4, 2012 (gmt 0)
The whole idea of a rewrite (as opposed to a redirect) is that the URLs used "out there" on the web do NOT change. This avoids having to redirect requests and it avoids having to alter links on pages.
New posts should also continue to use the old URL scheme. So to your rewrite:
RewriteRule ^(([0-9])([0-9])[0-9]+)\.jpg /$2/$3/$1.jpg [L]