No, the most loyal users won't abandon it. They will scream and curse and complain and beg you to make it the way it was for about four weeks. After that time, everyone will have forgotten what the old version looked like and stop complaining.
This hasn't been the case for the recent thesixtyone redesign. Hundreds of dedicated users (users who actually spent money) and artists have left and are more than likely never going back.
I'm not sure if this will pan out to be true and anyways they did the opposite of what this guy is doing. They took a usable site and made it unusable :)
Unless the redesign is a major step backwards, where you'll lose a lot of users with the redesign.
The website for the card game Magic:the Gathering is an example of that, they absolutely wrecked their webpage and forums, and I know that they lost a lot of forum users and webpage readers because of that (but maybe it's ok for them if they weren't the core audience).
I don't know if they did gain among the younger audience, so maybe the redesign was a success... I'll never know, as I'm not an insider.
I remember my outrage and all of the groups that formed when Facebook created the concept of the "News feed." Remember when to see the differences in people's profiles you had to individually check them?
Rinse, repeat, for every major redesign.