First off, Yoshi-P was the one who said that talked about limiting button bloat by replacing old abilities with new ones to maintain roughly the same amount of buttons. The changes to Thunder I/Thunder II/Thunder III demonstrate this mentality. He also said that tying all 51 to 60 abilities to Job Quests limited them and that in SB not all new skills/trait gain will be limited by Job Quest and some of them will be gained just by leveling.
Second, Foresight is likely gone because it fills the same design space as Rampart/Shadowskin: a 20s defensive buff with a 90s cooldown. Rampart/Shadowskin (-20% damage for 20s every 90s) effect seem to have been classified as "a skill that each existing and future tank must have access to in their skill pool" just like Provoke was early on. Rampart/Shadowskin becoming a Role skill means that Warriors do not need to have Foresight. Even though it works slightly different it is still in the same design space. Removing it frees up that design space that can be used to make Warrior more distinct. Foresight was also causing problems even though most players were not aware of them. Ever notice that def/mdef growth ground from 20/30 points every 10 ilevels from i150 to i210 to a near halt of 4 points per 10 ilevels at i215? Due to being tied to def, Foresight varied in effectiveness depending on gear ilevel.
Third the speculation was not necessarily wrong. The OP got blasted because many posters don't really get design or what the dev team is trying to do. Just because Foresight is slightly different than Rampart/Shadowskin doesn't mean that it is not getting replaced by role skill Rampart/Shadowskin.