I would almost bet money that it is not hardware limited. This is almost certainly a software issue.
I dont think some folks understand how a display actually works. Consider the fact that you can upload custom graphics to your HP-1. Download the default .bmp files from your HP-1, open them with Microsoft Paint, flip them upside down and save them. Now load them back to your HP-1.
They've already added the ability to change font sizes and whatnot. Again, the software is only manipulating what you see. How do I put this? The display is not "aware" of what is "up" or "down". It only knows that it is receiving a command to put X pixel in X location.
A display is only a slave to its driver (the software). For example, your PC is the same way. Many graphics drivers allow you to flip your Windows desktop, even skew it at an angle, or turn it exactly 90 degrees. I can do this even though I'm using a nearly 10 year old CRT.
And the fact that it is touchscreen doesnt change anything. When the display flips, the designated touch sensitive areas would move accordingly.