Well, do not worry, since the revised edition ("3.5.") was published*, no WotC book contains any "new core class".
The core classes are adept, arcane archer, arcane trickster, archmage, aristocrat, assassin, barbarian, bard, blackguard, commoner, cleric, dragon disciple, druid, duelist, dwarven defender, eldritch knight, expert, fighter, hierophant, horizon walker, loremaster, monk, mystic theurge, paladin, ranger, rogue, shadowdancer, sorcerer, thaumaturgist, warrior, and wizard.
No other D&D class is core. None.
* You may consider that arcane trickster, archmage, dragon disciple, duelist, eldritch knight, hierophant, horizon walker, mystic theurge, and thaumaturgist are new core classes from the original third edition.