Whatever the number, it's not gonna happen. Over the last few decades the trend has been to multi-role planes that can be used by both Air Force and Navy. Specialized ground attack planes like the A-10 aren't exactly en vogue these days. And even if they were, someone would insist that an A-10 replacement should be carrier-capable - something that's not not possible with a plane that matches the A-10 in armor, firepower, etc., far as I know planes. And even if that problem could be overcome, you'd never get the budget. With the F-35 touted as the plane for the future that is oh so versatile and superior, no one would want to admit that it leaves a gap in the arsenal at its hideously high cost.