It's heads up this Sunday. Phobos-Grunt is less than 24 hours away from reentering the Earth's atmosphere according to RIA the Russian news agency. The track for the possible debris impact zone is slowly narrowing as the time of reentry approaches. A recent post by @riascience on Twitter is,
"New #Roscosmos prediction for #PhobosGrunt decay date/time: Jan 15 14.36 UTC - 22.24 UTC"
The actual time of reentry is dependent on changing conditions in the upper atmosphere. One can get updates on the spacecraft descent and reentry at the following sites.
Spaceflight 101 Phobos-Grunt
The images at Orbit Ops Photos give updates on the spacecraft's altitude. The density of the atmosphere starts to rapidly increase as one descends down to about 80-90 km and the atmospheric drag then becomes significant. @riascience has been posting images of the location of the possible debris field along the spacecraft's track.
The website Zarya which covers Russian spaceflight and is maintained by a fellow of the British Interplanetary Society has been following recent predictions of the reentry time. One can see the uncertainties for the time is decreasing.