The only reason the OG Droid didn't get ICS in the dev community was because of the specs were out of date and couldn't handle ICS. This phone should be good for at least 2 years, no matter if it officially gets the update or not.
The Nexus One got one major update after it was released (Gingerbread), and will not get official Ice Cream Sandwich. So the Galaxy Nexus will get the "J" release, but not the release after that.
Sent from my Nexus S
It *might*. The reason why I say that is that it has plenty of RAM, a great processor, and capacious internal storage. Its definitely more 'future-proofed' than the Nexus One was. I could see them giving it two more releases and then that's it.
Regardless, I'll be on a different Nexus by the time the Galaxy Nexus no longer gets updated.