There are three options: Point [cpan://.....] to metacpan, add [metacpan://......], or wait and see if if the new sensation (which seems cool but does say "beta" in the top right corner) has the staying power and real-world popularity to become at least nearly as ubiquitous as search.cpan.org.
It might not hurt to add yet another link type, but there's the question of whether it will get used enough to justify the work. That could be proven here as a test bed, or the the Monastery could take the wait and see approach. I don't know which is better in this case. Perhaps it is a topic of discussion for cabal based on the response in this thread.
I do suspect that the notion of redirecting [cpan://...] to the metacpan site would probably not happen as it would alter the behavior intended by the authors of thousands of existing PerlMonks posts.