It looks like you can now convert your non-recurring Pro subscription to a recurring Pro subscription.

"Flickr Backpedals, Gives All Pro Users the Chance to Renew and Keep Their Benefits"
http://petapixel.com/2013/05/22/flic...heir-benefits/

"According to Flickr’s new FAQ page, eligible Pro users have three options: recurring users can continue renewing at the current price, non-recurring users can transition to a recurring Pro membership, and both recurring and non-recurring members have the chance to transition to the company’s new Free account and receive a prorated refund for the months they have left on their membership"

Eric