The questions that I want to know the answers to:
1. Will the next iterations of the iPad and MacBook(s) have this sort of display (perhaps as an option), or will it be the iteration after that?
2. How much will they cost?
1. Will the next iterations of the iPad and MacBook(s) have this sort of display (perhaps as an option), or will it be the iteration after that?
2. How much will they cost?
The iPad already reportedly falls pretty flat under conditions that tax the GPU's fillrate. Sextupling the amount of work that the GPU has to do likely wouldn't do the device any favors for performance or battery life, both of which are key marketing points.
Googling seems to indicate that the iPad has an A4 Mali GPU, which has a fillrate of about 100M pix/sec (by comparison, my desktop's Radeon 4850 has a fillrate of ~24 billion pix/sec). Each paint operation paints a certain number of pixels, and you'll do several of those per frame. At 1024x768 (786,432 pixels), the maximum fillrate-limited FPS to paint a one-pass single-color surface is about 127 FPS. Now, increase that to 2530x1898 (4801940 pixels) and your max FPS for the same operation drops to about 21 FPS - and that's just for painting a single color. Actually doing anything useful would utterly destroy the device. To compensate, they'd have to put in a beefier (more power-hungry) GPU. It's quite possible to build a device that would perform well at those specs, but it would be very expensive, and very difficult to fit into Apple's typical sexy form factors with any appreciable battery life.
(It's been a few years since I've done high-performance graphics work, so if I'm off here, someone please correct me.)
Now the only places to find them are extremely highend workstation laptops (aka. heavy, desktop portables)
You don't need the same level of DPI on the iPad and it would just take too much grunt to push the same DPI as the iPhone on that screen.