In order to upgrade your device to Android 4.0, the Ram of your device should be of a minimum of 256 Mb and it should have a decent GPU. The SE Neo and Arc can answer these demands easily, so no worries there!
Here's part of an article from
http://www.techradar.com/news/mobile-computing/android-4-0-ice-cream-sandwich-everything-you-need-to-know-954464
Android 4.0 Ice Cream Sandwich update
Google has confirmed it is working on an Android 4.0 update for the Samsung Nexus S and other Android devices.
Director of Android operating system User Experience Matias Duarte told Engadget that Google is. "Currently in the process for releasing Ice Cream Sandwich for Nexus S. Theoretically it should work for any 2.3 device."
Motorola confirmed to TechRadar that the Motorola Razr will launch in the UK with Android 2.3, but that there will be an update to 4.0in 2012.
I don't recommend upgrading your device, things could not run as smoothly as before! Either wait for the new phones to be released with the new Android OS or be satisfied with the v2.3!