So, the ipod Touch...
You've likely noticed, but my old buddy the ipod Touch is far behind the times. It's rocking three year old hardware, as it hasn't seen a refresh in about that long. Furthermore, its hardware; namely the screen and the battery, were gimped from the start. This is a significant fact, as Apple doesn't typically allow a well selling product to languish so long. The exception, of course, is when they have a substantial upgrade in the pipeline.
Now, there has been a lot of rumor, but nothing concrete. Some speculate that Apple will drop the ax on the Touch entirely, leaving the iPhone to take the full demand in that size range. Not an unreasonable assertion, given the facts. Others argue that Apple is waiting for its engineers to develop a more power efficient SoC before offering a refresh, due to the slimness of the existing form factor. Something based on a dual core A15, perhaps. Still others are whispering of a size increase; ranging from anywhere from 4.5 inches up to 7.85 inches. What resolution might such a device require? In what aspect ratio would it be presented? Would the chassis follow the lines of the past, or be radically different?
Let's get the obvious out of the way first. The iPhone and iPod Touch current stand at 3.5 inches, both sporting a resolution of 960 x 640 in an extremely odd aspect ratio of 3:2. Alternatively, the first two generations of iPad used a resolution of 1024 x 768 in a more standard 4:3 aspect ratio; which doubled to 2048 x 1536 for the current iPad. As you can see, Apple's current tactic of doubling display resolutions for more powerful hardware gives us something of a snarl when also factored with potential size increases and aspect ratio changes. The significant numbers presented by our various options stand thus:
1) The standard double at 960 x 640 at 3:2 gives us 1920 x 1280 at around 7 inches. Decrease the PPI slighty and Apple might get to a 7.85 inch display at 3:2 aspect with a PPI of 294. Not impossible at first glance. This option gives us respectable PPI and scaling for current apps. However, this resolution becomes much less likely if one considers the 4.5 inch form factor; as the pixel density becomes very high.
Standing odds: 45%
2) The scale down. There's been a lot of noise made about an iPad Mini. At first glance, admittedly unlikely; at least in name. But as a reborn iPod Touch, the possibility increases substantially. Merely take the old iPad resolution of 1024 x 768 at 4:3, name it the new iPod Touch and call it a day. Macrumors.com had a thread a while back expounding on the arguments in more detail.
Standing odds: 50%
3) With the iPhone rumored to be changing sizes and resolutions, we're given a new set of numbers to play with. If Apple moves to a more conventional aspect ratio of 16:9 (which Steve Jobs was known to have hated) and ~4 inches then that would plant it's resolution at 1136 x 640. This presents problems with our calculations, as simply doubling this resolution would leave us with 2272 x 1280. Apple can hardly offer a 7.85 inch device with with such a similar resolution to it's 9.7 inch iPad; and we can call readily conclude that such a resolution would be overkill at 4.5 inches.
Standing odds: 5%
Now, one could make a case for other resolutions; and even for Apple releasing products at both sizes. This is unlikely for the reasons mentioned earlier, and also for the simple fact that Apple would not risk diluting both the iPad brand and the iPod Touch brand at the same time. It has to be one or the other, at least at first. Thus, I conclude that we will see a new iPod Touch this fall. Whether it will fall into option one or option two, well, the odds are close.