I did a little math for you guys to break down the screen viability for ICS:
According to the Korean translation of the Samsung announcement, the HD display is indeed 16:9. With that aspect ratio, the display size is 1.5mm wider (3/4mm per side) than the traditional WVGA 4.3" screen. I'm sure they can make that up in the bezel so it won't affect your device width.
More importantly, the 1280x720 16:9 (1.78 aspect ratio) display would cause mapping issues vs WVGA (1.67 aspect ratio)....
....UNLESS....
....you maintain the WVGA aspect ratio in the viewable are on the new HD screen. That equates to 1200x720, leaving 80 pixels unused in the horizontal (phone in landscape orientation). Well, at 315ppi, 80 pixels equates to about 1/4", so if you skewed the fixed WVGA aspect ratio to the left, you'd leave a 1/4" space on the right side (or at the bottom of the phone in portrait orientation). Hmmmm. My Droid Charge buttons are ~0.25" tall. So now you have no legacy Android application mapping issues AND room for software buttons at the bottom of the screen, but you can still view HD movies in full aspect ratio if you hide those buttons. Interesting...eh?