Yep, my Hosting Facility has already gone down that path.
FWIW, here are snippets of updates I have received from the president of my Hosting Facility:
[07-31-2105] "I've heard back from cpanel... It looks like this issue is known and already has a case open with cPanel. They are working with their developers in order to find a fix for this now."
[08-05-2015] "This is the latest regarding the address books from my Chief Engineer who has continued to work on this issue. Here is what he wrote: 'I received confirmation that this was a known internal issue at cPanel. I was just told their developers and QA Department will be having a meeting about this issue tomorrow afternoon, and we will hopefully have a game plan to resolve this issue after the fact. We'll make sure to update you again once we have more information' "
[08-06-2015] "Following the meeting at cPanel yesturday, it looks like the devs are orking on a solution for this now. Their plan is to get it working for cPanel 11.52 and then back port the patch for earlier versions as well. Once that patch is working, they'll fix the yourdomain.com account, and update us again through our ticket. Sorry about this issue. It is above and beyond our control."
It would have been nice to have been informed by CPanel that this is a known problem within Horde's most-recent roll-out, that an internal ticket in CPanel had previously been issued, and that the Devel team has at least given lip service to fixing it. But maybe you are not privvy to that information? Apparently our installation is not the only one which had address books vanish. Not to mention that user-control folder logic and preferences have been obliterated by the most recent update.
Horde is doing a fabulous job of re-defining itself as an also-ran to RoundCube. RoundCube is clearly the platform towards which my people will migrate.