I don't have any links on-hand, but I remember in many posts from even before HW came out with info that the only reason we don't have Samurai right now is because they were deciding between it and Dark Knight (which made the cut). To many this points to Samurai being highly likely to come with 4.0. If there is more actual info on this I do not know.

Red Mage I believe was also discussed by devs, and as said in some other threads (like the one about general speculation of future jobs I believe), Red Mage is the only original FF job not yet in this game. If we continue to get three jobs per xpac Red Mage also has a good chance of being added in the next one.