There's probably the very slim chance that if two Sorcerers cast Negate within range at the exact same time, they'd both be silenced and cancel each other's Negate out. Ultimate spent but no lasting effect for either.
But much more likely, one will cast ever so slightly faster and that one would be the dominant area effect.
You'd need a really controlled and precisely timed environment to even test this. Almost like creating an artificial element for a fraction of a second.