We were a bit puzzled by the statement from Hugo Barra, Google's product manager for mobile, regarding the fact that the Nexus S would run Ice Cream Sandwich but not the Nexus One because it was too old; we were left literally scratching our heads because on paper at least, they are almost identical.
Both come with 512MB RAM, a WVGA resolution and a five megapixel rear camera. The Nexus S comes with the Cortex A8 based Samsung Hummingbird chipset (clocked at 1GHz) while the Nexus One boasts a Qualcomm QSD8250 Snapdragon chipset, also clocked at 1GHz.
The only major differences between the two handsets are that the Nexus S has a secondary front facing camera, more onboard storage, doesn't have a microSD card slot, and has a bigger screen.
We're therefore not sure why the Nexus One will not get ICS while the Nexus S will. As one of our readers puts it, the hardware may be two years old but the specification should be more than enough to handle it, especially given the fact that the Nexus One doesn't come with any proprietary user interfaces (like HTC's Sense or Motorola's Motoblur). Anyway, we can always count on someone from XDA Developers to release a custom ROM sooner or later.