User blog comment:Master Sima Yi/Assassinews 05-08-'14 – Assassin's Creed: Rogue announced/@comment-41.69.147.157-20140806015457/@comment-13471981-20140806145112

While it's true that being a Templar does not mean there won't be a Hidden Blade (let's face it, that thing is far too iconic not to have), I don't imagine many Templars were walking about with Hidden Blades strapped to their wrists. There might be some unorthodox collectors like du Casse but I doubt they were being used - unless we're talking about the turncoats you mentioned, who would have been trained in the Hidden Blade's use.