Any particular reason you think Firefox won't also implement Google's HSTS preloads for .dev?
Google owns that TLD, so I don't see why any browser which supports HSTS preloads would choose to ignore that particular pin, especially given that a move towards universal deployment of HTTPS is generally regarded as a good thing by browser developers and security experts.
Google owns that TLD, so I don't see why any browser which supports HSTS preloads would choose to ignore that particular pin, especially given that a move towards universal deployment of HTTPS is generally regarded as a good thing by browser developers and security experts.