NASA is unrelated to the eye tracking.

You don't work with Nintendo either.

I work in a studio mate.

secretaries dont count

Secretaries dont know Ruby.

It depends on the game. The biggest thing is if i notice drops. Other besides that 1080 all the way. Lucky we are close to having the best of both worlds at launch, it will only get better from here out.

Outside of fighting games, 1080p easily.

Graphics cards can only move data so fast.  You could move four times the amount of data in a 720p/30fps game than you can in a 1080p/60fps game, making it potentially four times better looking.  Well, not exactly four times because you'd have to take away from the degradation you receive losing 1080p.  The game might also be designed to reduce screen size, so removing 1080p resolution might zoom everything in by two, it'll look the same aside from everything being zoomed in(which I actually don't like in games.)

Depends what they want to do. Dead Rising 3 could run at 1080p and 60FPS if they cut out half the Zombies on screen. Sometimes having none of it isnt a bad thing.

I would choose Framerate over resolution because anything higher then 720p is sharp enough.

To come back to the gaze tracking, if it can work without noticeable lag, rendering 2 x 720p can net you the illusion of full 4K resolution.
Render 1 big picture in 1280x720, upscale it x 3 to 3840x2160. Render a detailed rectangle where you are currently looking, also at 1280x720 and put that at 1:1 pixel mapping on top of the upscaled image in the right place. Add some nice blending around the edges and the eye should not be able to tell the difference as long as you sit close enough to have a 30 degree field of view of the display. Which would be sitting at 1.6 times the diagonal screen size, for example max 8ft from a 60" 4k display, or 3ft from a 24" 4K monitor.

That's still 11% less pixels to render then 1080p (although it involves some upscaling and blending) With eye tracking 4K doesn't have to cost anything over 1080p rendering.

Scale it back to 1080p displays, take 2 640p images to create 1080p60 at the same cost as full 1080p30. And it shouldn't mattter if you sit upto 2.5 x diagonal away from the display. (9 ft from a 42" 1080p screen)

It will look weird to onlookers though, but such a 4k illusion mode is in reach with current consoles.

Gameplay "feel" depends much more on fps than on resolution so to me this is a no-brainer.