For the people that are having a hard time grasping a 4.6 inch screen on a phone, I decided to cut out a piece of paper to the exact dimensions of this display, and place it over my Thunderbolt to show how small of a difference it actually is.
There are lots of calculators online that can calculate the exact dimensions of a screen for you, I use this one...
DPI Calculator / PPI Calculator
You can't calculate length and width of a display with just the diagonal length unless you have the aspect ratio or resolution, fortunately we know that this display will mostly likely be 720p (or 720 wide by 1280 tall - in portrait mode that is), so we can easily calculate the exact dimensions of the screen. The cool thing about these calculators too is that if you know the diagonal length and the resolution you can also calculate the pixel density.
Also it's worth mentioning that when comparing displays on two different phones, even when the diagonal length is the same, if they have don't have the same aspect ratio they will have different dimensions, for example the Droid X and Droid X2 (both 4.3 inch) are 16:9 since the resolution is 480 x 854 (Droid X), and 540 x 960 (Droid X2), so those two displays have the same exact dimensions however the Thunderbolt, which is also 4.3 inch, is 5:3 (15:9 if you do the math) since the resolution is 480 x 800, meaning that when you compare the Droid X or X2 with the Thunderbolt you'll notice the display on the Droid X / X2 is actually a bit skinnier and longer (more rectangular) where as the Thunderbolt is a little bit wider and shorter (more square), although the difference isn't as dramatic as it sounds.
So, using the calculator we can find the exact dimensions of the Thunderbolt's display and compare it to the dimensions of the rumored Nexus Prime's display...
Thunderbolt - 4.3 inch, 480 x 800 = 2.21" (W) ?— 3.69" (H) - with 216.97 ppi
Nexus Prime - 4.6 inch, 720 x 1280 = 2.26" (W) ?— 4.01" (H) - with 319.26 ppi
So as you can see the difference in length (vertically in portrait) is about .32 inches (4.01 - 3.69) , and the difference in width (horizontally in portrait) is a mere .05 inches (2.26 - 2.21).
Here are the pictures...
With the first picture, I merged two photos with both screens aligned at the top left corner to show the difference in length and width of the screens...
Here I centered the paper more around the bezel to show how much room they could have and still keep the same form factor.
Sorry for the long post..