I haven't heard this through my normal sources, but through two other sources, one private and one Father Zuhlsdorf, there is speculation about December 8th, the Feast of the Immaculate Conception, in regard to the Motu Proprio.
"With my luck, just because I will be out of Rome for a little trip with a priest friend on 8 December, I predict that that is the day the document will be released. No doubt I will get am SMS on my cellphone telling me something is up when I am out on the road without internet access. Just watch."