Click packages up to now have been the new packaging format used by Ubuntu Touch/Phone that is designed to boast simplified packaging that ties in well with the Ubuntu SDK. The Click packages also are able to run within a confined environment under greater security than traditional Debian packages. Click packages are preferred in the Ubuntu Touch/Phone space and used in place of Debian packages. Within the Ubuntu desktop space, they are coming to complement Debian packages and will not outright replace APT -- at least for the foreseeable future.
Click packages for the desktop were discussed Wednesday during the latest Ubuntu Online Summit. Click packages are being brought to the desktop for their confinement/security advantages, interest from upstreams, the ability to ship new releases whenever desired, rollback support, and is necessary for Ubuntu's "convergence" vision of running apps across form factors.
For Ubuntu 14.10, developers will investigate potentially using PackageKit, command-line hooks for register Click apps, and other changes. Click packages though won't come into full benefit though until Mir / Unity 8 come into play on the Ubuntu desktop for realizing the convergence vision and better interoperability with the Ubuntu Touch/Phone components.
More information on the Click work for Ubuntu 14.10 can be found via this session page and the video that's embedded below.