As you may know, Ubuntu Touch 1.0 will be released on October 17, the same day as the Ubuntu 13.10 Saucy Salamander release.
Because Apparmor is blocking other applications from accessing the contacts, third party developers will not be able to create chat applications for Ubuntu Touch.
The Canonical developers will not change this for Ubuntu Touch 1.0, so the chat applications will need to use their own contacts, because the global ones are not accessible.
As a reminder, Ubuntu Touch is the mobile version of Ubuntu 13.10 Saucy Salamander, and will be released with official support for the Google Nexus smartphones and tablets. Despite that, it has been experimentally ported on both OPPO Find 5 and Xperia Tablet Z.
Among others, Ubuntu Touch will come with an optimized version of Evernote, and a set of applications developed by third party developers, under the supervision of the Canonical team, called the Ubuntu Touch Core Apps.