I haven't seen any sort of mass exodus from Wacom in the pro market yet. Wacom makes highly specialized hardware for graphics professionals. I don't think any fly by night piece of prosumer hardware is going to make them lose TOO much sleep.
Additionally, I think they'd likely be far more concerned if Apple released an iMac like this (which I wish they would). Reason being, most graphics pro's are already on iMacs and if they suddenly had the drawing capabilities and form factor built into their go-to system, they might have less of a need for an additional piece of hardware (Cintiq, Intuos). Apple is known to pay attention to the kind of details artists care about in implementation.
