We have to completely rewrite the PayPal Pro gateway for PayFlow. It is currently using Website Payments Pro. It's basically like having to redo the gateway from scratch which is already a time consuming and expensive task (it takes significant development hours). It's a bit trickier than that though since they're 2 different APIs with different API keys we have to basically support both APIs unless PayFlow absolutely for sure has backwards compatibility for Website Payments Pro. We do have plans to do this, but I don't know as to when. Will review next week since I've just cleared CB AntiSpam 3.1.0 off my task list.