Recently one of my Gmail contacts changed her picture on Google+. This change came through immediately in the web version of Gmail, but after days it still hadn’t found its way to the contact on my phone.
It seems that the issue is that Gmail (or Android?) doesn’t consider a Google+ picture change to be a change in the contact itself. In order to get this to flow down to my phone, I simply edited the Notes field in the Gmail (web) contact. Within seconds the picture (and Notes field) were updated on my device.
Google: Please fix this. I shouldn’t have to “touch” a contact when their G+ picture changes. It should just flow down to all my Googley devices.