Remap Django Templates is a very simple plugin that does exactly what the title suggests: it remaps the syntax highlighting for all HTML files to Django Template.
Installation is very simple. Just copy the remap_django_templates.* files to your
gedit plugins directory (usually found at ~/.gnome2/gedit/plugins):
git clone http://github.com/dguaraglia/gedit-django-template-remapper
cd gedit-django-template-remapper; cp remap_django_templates.* ~/.gnome2/gedit/plugins
then enable the 'Remap Django Templates' plugin in gedit by going to Edit->Preferences->Plugins.