Most ARM hardware -- including smart-phones and tablets -- tend to only support OpenGL ES rather than the full desktop OpenGL implementation. If game developers target the common sub-set of OpenGL shared with OpenGL ES, it's a win for both mobile and desktop gaming.
Ubuntu developers themselves don't plan to do much game/software porting to OpenGL ES, but rather are looking for the community to become involved. From a session held in Copenhagen this week for the Ubuntu Developer Summit, "The Ubuntu archive is full of exciting GL games. Many of these games are likely runnning fine on arm if they are built with the right flags to enable GLES support. We are looking for community members to assemble a list of possible candiates for this, submit package fixes and get them sponsored into the archive by an Ubuntu dev."
Among the action items coming out of the OpenGL ES gaming discussion at UDS are to check that the Debian games team will accept OpenGL ES patches for their packages, seeing what games already in the Debian/Ubuntu archive can already be toggled at build-time with OpenGL ES support, a new GLES-enabled version of supported games, look for Linaro GLES game patches, look for any Maemo OpenGL ES patches, and look for patches done by the OpenPandora community. There's also hope that more games will begin to utilize Waffle for run-time selection of the GL/GLES version as well as switching between the windowing system so one binary can work on both X11 with GLX and Wayland with EGL.