I listened to the podcast where they tried to explain it, but really, they didn't explain it. They just basically said "Every party will need a wizard just like every party needed a cleric ('they'll have to use different tactics'), mostly because we thought we needed an iconic mix of classes rather than to allow two choices for controllers."
It's couched in some catchprase-speak, but still, every party will need a wizard in 4e as much as every party needed a cleric in 3e.
They need to stop bragging about how they've "solved" this problem in 4e. They didn't. They've shifted it onto a different role, a different class, but for any ideal party, someone will still "have" to play the Wizard.
/mild annoyance