If WotC doesn't publish new classes these will be created by 3PPs.
I think there is enough space for classes with special game mechanics, as the psionic powers, but also the martial adepts (Tome of Battle: Book of Nine Swords), with martial maneuvers, powers in the middle between at-will and once-encounter, the vestige binder, and the incarnum totemist shaman, with incarnum soulmelds as added monster traits (natural weapons, breath attack..). Maybe the rune scribe would be a incarnum soulmelder class, with powers on runes in the chakras (body slots for magic item).
Only one class, the artificer, has been added. After the psionic mystic and the martial adepts (crusader, warblade and swordsage) WotC can allow itself some pieces more of crunch in a far future. And the last years of an edition are perfect to test new ideas without worrying too much if fandom likes it or doesn't.