I am trying to get an idea if indexers like Zeitgist or Nepomuk are in active use by the various desktops or are they being phased out and replaced?

Most of the documentation online for these seem to be a year or three old, which might indicate that they are not in active development.

What does KDE use now and what are the plans for the next year or so?
Same with Gnome, Unity, LXDE. Where are they going in the next year?

Ubuntu 14.04 will be a LTS support release, so it would be good to know what it's fundamental indexing technology will be.