is it totally necessary to have people reply to this thread and say they have the issue too? I think that needs to stop and in future we only want to see actual results/tests/solutions. thanks.
Firstly it's a forum and sometimes an important part of fault finding is understanding how many people the issue effects, and none of your post here was a result/test/solution!
Anyway I have been having contact display and syncing issues ever since I did a batch of updates of contacts on my Mac 2 weeks ago...
After some playing about today I put it down to the following error I could see in log console:
fault 19:05:10.926650 +0000 AddressBookSourceSync CGImageSourceCreateWithData:2940: *** ERROR: CGImageSourceCreateWithData: data is nil
When I was updating contacts on my mac I also updated quite a few contact images, it would appear that contact sync could not find the image to sync up to iCloud so was whole sync was getting stuck. I think it maybe happened because I deleted one of the pictures I used for a contact right after assigning it, so the source image was not there when trying to sync it to iCloud.
Anyway I ran through all the contacts that I had updated the picture on the mac and selected the contact -> card -> clear custom image. Then the contact sync started working again to iCloud and opening iMessage on all devices started showing proper contact details again.
Now I understand that this might not be the fix in this case but one of my symptoms was the same so I would suggest opening the log console on the mac search for AddressBookSourceSync and see if there are any messages that point to the cause.