Couldn't it be some sort of new notification system for the driver which gives him instinctive feedback and lets him drive the engine the same way traction control would?
"Any device or system which notifies the driver of the onset of wheel spin is not permitted."
The drivers are extraordinarily focused professionals during races. I can't imagine adding some signaling system that would let the driver react any faster than he already was.
I am not confident that they have cheated either.
The problem is that you'd need to be right almost every single time - a single slightly wrong prediction could quite easily cause a crash.
Ultimately, I doubt that such a system (one which relies on the drivers' reaction to a TCS notification) would really gain very much. These drivers are already incredibly experienced, they have a team of professionals poring over their telemetry, and thus they are already using a sort of "traction control," albeit completely manually.