I imagine they won't be saying much.
Remember, this was a political operation from the git-go, in which the Mexican government was fully complicit and its leading politicians fully engorged and tingling, to pin the blame for Mexican violence and mesoscale death and destruction on American citizens and our Bill of Rights, in order to get the BoR changed and our RKBA impugned, vilified, and finally extinguished by legislation, U.N. treaties, and executive orders.
The Mexican government's gradually fading LE resources are the only thing between these journalists and the cartels. They won't be exposing any current or past presidents of Mexico on F&F.
The Mexican government cooperated in Wide Receiver, which was a classic sting operation and had forces from both the US and Mexico involved in monitoring and tracking the criminal gang networks that sold guns to the Mexican drug gangs.
Fast and Furious did not have the cooperation of the Mexican government because, in fact, it couldn’t have, since the Mexicans would have prevented these guns from reaching the drug gangs. The whole point of Fast and Furious and its covert nature was to ensure that the guns distributed by the ATF made it to the streets and were used in killing people (you know, those insignificant little tan people - Obama has nothing but contempt for Mexicans), whose deaths could then be used to provide support for Obama’s gun-control laws.