I can confirm that the changes that were in the air have happened:
the Ministry of Cultural Affairs has changed the # of free museum days, actually increasing them from 12 to 20 per year.... but the first Sundays of the month have been reduced, they will only be offered for the months of October through March only. It makes sense, those are the months when there are less visitors to the country and thus they want to encourage more locals to go and those that come in lower season. Those that come in high season will have to pay.
However, the museums will decide when and why to have other free museum days, so there won't be a uniform calendar, aside from a whole week of free museums, currently going on right now (March 5-10).