The fourth-generation iPod touch contains an Apple A4 SoC with 256 MB of RAM, the same internals as the original iPad. The original iPad has already been cut out of the iOS software update schedule, but the fourth-generation Touch did get iOS 6. This is probably because the Touch has less pixels to push around, because it has a slightly lower screen resolution than the iPad, which meant it could just about cope.
However, cutting off the original iPad was a clear signal that the Touch was soon to follow the same fate, because the hardware is so alike. The timing of introduction of this fifth-generation device (and thereby removing all fourth-generation Touch’s from sale) makes this foreshadowing a near-certainty. iOS 7 will not run on a fourth-generation Touch, and probably not on the iPhone 4 either, as that is also due to be cut off.