I don't know about that. OG droid got GB way before the X2 did. You'd THINK the newer phones would have priority on new updates, but that doesn't always seem to be the case. I think I got Froyo on my Eris before it was released to a lot of other phones. Then again, I didn't know much about phones back then so I might be remembering wrong.
I have also heard ICS and the Bionic were made for eachother. Though I'm also surprised there was such a huge gap (like a year, right?) between Froyo and GB, but ICS phones are coming out in a few months. Maybe GB was a transition OS to find the middle ground between single/dual core phones. Maybe only dual core phones will get full ICS, singles will get a new GB? Who knows...