Of course I am talking about right now. Why would someone want to sign up for a service that they could "possibly" use several years from now? The wonderful thing about analytics is that it doesn't affect the user experience. If you user knows that a camera is going to be turned on when they visit your website, your user activity is going to drastically drop. Not to mention you are relying on the fact that not only will it be adopted by users as "acceptable" but also adopted as a pre-packaged hardware. Otherwise, you are going to have a difficult time convincing end-users to purchase an eye tracking device that they won't personally use.

The only way that this would be remotely feasible is if you were able to remotely turn on a user's camera - which won't happen and wouldn't be taken lightly by the end-users.

Ofcourse - all of this doesn't include the cost of awareness that it would take just to make remote use of eye-tracking. You say "tens of thousands" of eye trackers are on the market. With 7billion+ people in the U.S., it's highly likely that you wouldn't receive one person using an eye tracker in the next 10 years - in which you would need hundreds just to make a reasonable estimate on potential site adjustments.

I get what you are trying to do, but the market just isn't there. A better way would be user predictions - or predicting user actions and engagements. That technology is around but not heavily used yet in analytics and would be able to make similar predictions.