ICS will be completely improved compared to 2.x (utilizes hardware acceleration, no more laggy homescreen transitions, will be @ 60fps constant). That being said, its just an OS, and can be installed on any compatible Android, whether manufacturers/carriers are punctual or not, by a process called rooting. So, get your phone when you feel like getting one, or when you find the one you like. Now, xmas, new year, whenever. ICS will end up on it regardless.
If you end up waiting, remember that it would be for better hardware, not software. Good luck!
If you end up waiting, remember that it would be for better hardware, not software. Good luck!