It's certainly true that 747 freighters have been busy lately, for example yesterday there were around 25% more flights by 747Fs than by, say, 777Fs.
But that's offset by pax 777s (obviously carrying belly cargo and many with some freight upstairs too), which operated around 20 times as many flights as the small number of pax 747s left.
So in terms of total lift, there's probably not much to choose between the respective contributions of the two types.