I can assure you they will NOT change the resolution. They chose the current resolution because it was the exact double of the old iPhone and same as the iPhone 4. This is to ensure all old apps will work on the device since it's easy to stretch the graphics to double the size. Also, this meant a lot of people had to adjust their apps to take advantage of the new resolution. Changing resolution again means that tens of thousands of apps will have to be changed again, or exist in several different versions. And no, before you ask, scaling an app to a decimal scale or another aspect ratio would look awful. I really don't believe Apple would put the app developers through such a hell.
I guess the resolution will be the same for a long time to come. Perhaps they will double it again in the future since that's the simplest way, but the hardware in the iPad today don't have hardware to deliver smooth motion to a 2048x1536 screen.
They must have some plan for the future developments they can't stay the same size forever. There is only so many other features they can add over time without changing the screen. There are many options for how Apple moves the screen forward over time. Most of them will require developers to do some work to take advantage of.
So I wouldn't rule it out but I couldn't see them going 1260x768 on the iPad unless the app's space stayed the same res and the screens extra area was reserved for the multitasking dock which would always stay on the short edge when not used for video playback or extra room for the keyboard is active. Then maybe take the button off the iPad, to keep the size the same.
All that said I could see them moving to a screen with a low power ereader mode first before changing the screen resolution. That would expand the range of the device, not just for outdoor use, but for a lot of business applications as well. Plus give major usage life if keep the backlight off. Still that would require developers to do some adjustments to their app to decide if the mode was suitable and if the user can switch between.