SSL and Recurring subscribers and PayPal IPN's

We are moving our site from an unsecured environment over to a secured SSL one. If we had subscribers sign up with membership pro under a recurring subscription through PayPal utilizing IPN's and then force all traffic to https will the existing IPN's in PayPal still function or will we need to redirect them or something. I have successfully tested new signups in the secured environment and they work but I am concerned about existing users and their IPN's that are already setup in PayPal directed at http versions of the site. Thank you.

It should still work well even if you don't setup the redirection. Could you please confirm that currently, access to a link on http mode still works OK? Mean both http and https work well?

Tuan