First off I would love to see samurai but with that said, it will not happen in 3.0. Bring samurai to the game would bring a whole back story that SE would not blow just for one class. It will further bring closer to ninja story which I would see in a expac. Second Yoshi already stated same WILL be a DPS not a tank.

With HW they said DRK and SAM were both choices they had to choice which would go in game. The dev team looking back on previous FF titles, not just FFXI ,said sam in previous titles does not fit the tank role or the vibe of HW. It is a class planned for future release but nothing at the moment. Personally I woke up early last year when TGS was going on hoping SAM would be the secret class released but they went with dark and I died a little in side lol.

With the move into HW I would not be surprised if they added another class it not being a caster but at the same time I do not see them adding it. They will hold off til next year so players can get to a happy middle with the current classes and master them.